The QString class provides a Unicode character string.
QString stores a string of 16-bit QChars, where each QChar corresponds one Unicode 4.0 character. (Unicode characters with code values above 65535 are stored using surrogate pairs, i.e., two consecutive QChars.)
Unicode is an international standard that supports most of the writing systems in use today. It is a superset of ASCII and Latin-1 (ISO 8859-1), and all the ASCII/Latin-1 characters are available at the same code positions.
Behind the scenes, QString uses implicit sharing (copy-on-write) to reduce memory usage and to avoid the needless copying of data. This also helps reduce the inherent overhead of storing 16-bit characters instead of 8-bit characters.
In addition to QString, Qt also provides the QByteArray class to store raw bytes and traditional 8-bit '\0'-terminated strings. For most purposes, QString is the class you want to use. It is used throughout the Qt API, and the Unicode support ensures that your applications will be easy to translate if you want to expand your application's market at some point. The two main cases where QByteArray is appropriate are when you need to store raw binary data, and when memory conservation is critical (e.g., with Qt for Embedded Linux).
One way to initialize a QString is simply to pass a const char * to its constructor. For example, the following code creates a QString of size 5 containing the data "Hello":
QString str = "Hello";
QString converts the const char * data into Unicode using the fromAscii() function. By default, fromAscii() treats character above 128 as Latin-1 characters, but this can be changed by calling QTextCodec::setCodecForCStrings().
In all of the QString functions that take const char * parameters, the const char * is interpreted as a classic C-style '\0'-terminated string. It is legal for the const char * parameter to be 0.
You can also provide string data as an array of QChars:
QString makes a deep copy of the QChar data, so you can modify it later without experiencing side effects. (If for performance reasons you don't want to take a deep copy of the character data, use QString::fromRawData() instead.)
Another approach is to set the size of the string using resize() and to initialize the data character per character. QString uses 0-based indexes, just like C++ arrays. To access the character at a particular index position, you can use operator[](). On non-const strings, operator[]() returns a reference to a character that can be used on the left side of an assignment. For example:
For read-only access, an alternative syntax is to use the at() function:
QString str;
for (int i = 0; i < str.size(); ++i) {
if (str.at(i) >= QChar('a') && str.at(i) <= QChar('f'))
qDebug() << "Found character in range [a-f]";
}
The at() function can be faster than operator[](), because it never causes a deep copy to occur. Alternatively, use the left(), right(), or mid() functions to extract several characters at a time.
A QString can embed '\0' characters (QChar::Null). The size() function always returns the size of the whole string, including embedded '\0' characters.
After a call to the resize() function, newly allocated characters have undefined values. To set all the characters in the string to a particular value, use the fill() function.
QString provides dozens of overloads designed to simplify string usage. For example, if you want to compare a QString with a string literal, you can write code like this and it will work as expected:
You can also pass string literals to functions that take QStrings as arguments, invoking the QString(const char *) constructor. Similarly, you can pass a QString to a function that takes a const char * argument using the qPrintable() macro which returns the given QString as a const char *. This is equivalent to calling <QString>.toLocal8Bit().constData().
Manipulating String Data
QString provides the following basic functions for modifying the character data: append(), prepend(), insert(), replace(), and remove(). For example:
If you are building a QString gradually and know in advance approximately how many characters the QString will contain, you can call reserve(), asking QString to preallocate a certain amount of memory. You can also call capacity() to find out how much memory QString actually allocated.
The replace() and remove() functions' first two arguments are the position from which to start erasing and the number of characters that should be erased. If you want to replace all occurrences of a particular substring with another, use one of the two-parameter replace() overloads.
A frequent requirement is to remove whitespace characters from a string ('\n', '\t', ' ', etc.). If you want to remove whitespace from both ends of a QString, use the trimmed() function. If you want to remove whitespace from both ends and replace multiple consecutive whitespaces with a single space character within the string, use simplified().
If you want to find all occurrences of a particular character or substring in a QString, use the indexOf() or lastIndexOf() functions. The former searches forward starting from a given index position, the latter searches backward. Both return the index position of the character or substring if they find it; otherwise, they return -1. For example, here's a typical loop that finds all occurrences of a particular substring:
QString str = "We must be <b>bold</b>, very <b>bold</b>";
int j = 0;
while ((j = str.indexOf("<b>", j)) != -1) {
qDebug() << "Found <b> tag at index position" << j;
++j;
}
QString provides many functions for converting numbers into strings and strings into numbers. See the arg() functions, the setNum() functions, the number() static functions, and the toInt(), toDouble(), and similar functions.
To get an upper- or lowercase version of a string use toUpper() or toLower().
Lists of strings are handled by the QStringList class. You can split a string into a list of strings using the split() function, and join a list of strings into a single string with an optional separator using QStringList::join(). You can obtain a list of strings from a string list that contain a particular substring or that match a particular QRegExp using the QStringList::find() function. :
Querying String Data
If you want to see if a QString starts or ends with a particular substring use startsWith() or endsWith(). If you simply want to check whether a QString contains a particular character or substring, use the contains() function. If you want to find out how many times a particular character or substring occurs in the string, use count().
QStrings can be compared using overloaded operators such as operator<(), operator<=(), operator==(), operator>=(), and so on. Note that the comparison is based exclusively on the numeric Unicode values of the characters. It is very fast, but is not what a human would expect; the QString::localeAwareCompare() function is a better choice for sorting user-interface strings.
To obtain a pointer to the actual character data, call data() or constData(). These functions return a pointer to the beginning of the QChar data. The pointer is guaranteed to remain valid until a non-const function is called on the QString.
Converting Between 8-Bit Strings and Unicode Strings
toLatin1() returns a Latin-1 (ISO 8859-1) encoded 8-bit string.
toUtf8() returns a UTF-8 encoded 8-bit string. UTF-8 is a superset of ASCII that supports the entire Unicode character set through multibyte sequences.
toLocal8Bit() returns an 8-bit string using the system's local encoding.
As mentioned above, QString provides a lot of functions and operators that make it easy to interoperate with const char * strings. But this functionality is a double-edged sword: It makes QString more convenient to use if all strings are ASCII or Latin-1, but there is always the risk that an implicit conversion from or to const char * is done using the wrong 8-bit encoding. To minimize these risks, you can turn off these implicit conversions by defining the following two preprocessor symbols:
QT_NO_CAST_FROM_ASCII disables automatic conversions from ASCII to Unicode.
QT_NO_CAST_TO_ASCII disables automatic conversion from QString to ASCII.
One way to define these preprocessor symbols globally for your application is to add the following entry to your qmake project file:
Similarly, you must call toAscii(), toLatin1(), toUtf8(), or toLocal8Bit() explicitly to convert the QString to an 8-bit string. (Other encodings are supported through the QTextCodec class.)
Note for C Programmers
Due to C++'s type system and the fact that QString is implicitly shared, QStrings may be treated like ints or other basic types. For example:
QString Widget::boolToString(bool b)
{
QString result;
if (b)
result = "True";
else
result = "False";
return result;
}
The result variable, is a normal variable allocated on the stack. When return is called, and because we're returning by value, the copy constructor is called and a copy of the string is returned. No actual copying takes place thanks to the implicit sharing.
Distinction Between Null and Empty Strings
For historical reasons, QString distinguishes between a null string and an empty string. A null string is a string that is initialized using QString's default constructor or by passing (const char *)0 to the constructor. An empty string is any string with size 0. A null string is always empty, but an empty string isn't necessarily null:
All functions except isNull() treat null strings the same as empty strings. For example, toAscii().constData() returns a pointer to a '\0' character for a null string (not a null pointer), and QString() compares equal to QString(""). We recommend that you always use the isEmpty() function and avoid isNull().
Argument Formats
In member functions where an argument format can be specified (e.g., arg(), number()), the argument format can be one of the following:
Format
Meaning
e
format as [-]9.9e[+|-]999
E
format as [-]9.9E[+|-]999
f
format as [-]9.9
g
use e or f format, whichever is the most concise
G
use E or f format, whichever is the most concise
A precision is also specified with the argument format. For the 'e', 'E', and 'f' formats, the precision represents the number of digits after the decimal point. For the 'g' and 'G' formats, the precision represents the maximum number of significant digits (trailing zeroes are omitted).
More Efficient String Construction
Using the QString '+' operator, it is easy to construct a complex string from multiple substrings. You will often write code like this:
QString foo;
QString type = "long";
foo->setText(QLatin1String("vector<") + type + QLatin1String(">::iterator"));
if (foo.startsWith("(" + type + ") 0x"))
...
There is nothing wrong with either of these string constructions, but there are a few hidden inefficiencies. Beginning with Qt 4.6, you can eliminate them.
First, multiple uses of the '+' operator usually means multiple memory allocations. When concatenating n substrings, where n > 2, there can be as many as n - 1 calls to the memory allocator.
Second, QLatin1String does not store its length internally but calls qstrlen() when it needs to know its length.
In 4.6, an internal template class QStringBuilder has been added along with a few helper functions. This class is marked internal and does not appear in the documentation, because you aren't meant to instantiate it in your code. Its use will be automatic, as described below. The class is found in src/corelib/tools/qstringbuilder.cpp if you want to have a look at it.
QStringBuilder uses expression templates and reimplements the '%' operator so that when you use '%' for string concatenation instead of '+', multiple substring concatenations will be postponed until the final result is about to be assigned to a QString. At this point, the amount of memory required for the final result is known. The memory allocator is then called once to get the required space, and the substrings are copied into it one by one.
QLatin1Literal is a second internal class that can replace QLatin1String, which can't be changed for compatibility reasons. QLatin1Literal stores its length, thereby saving time when QStringBuilder computes the amount of memory required for the final string.
Additional efficiency is gained by inlining and reduced reference counting (the QString created from a QStringBuilder typically has a ref count of 1, whereas QString::append() needs an extra test).
There are three ways you can access this improved method of string construction. The straightforward way is to include QStringBuilder wherever you want to use it, and use the '%' operator instead of '+' when concatenating strings:
#include <QStringBuilder>
QString hello("hello");
QStringRef el(&hello, 2, 3);
QLatin1String world("world");
QString message = hello % el % world % QChar('!');
A more global approach is to include this define:
#define QT_USE_FAST_CONCATENATION
and use '%' instead of '+' for string concatenation everywhere. The third approach, which is the most convenient but not entirely source compatible, is to include two defines:
This operation takes constant time, because QString is implicitly shared. This makes returning a QString from a function very fast. If a shared instance is modified, it will be copied (copy-on-write), and that takes linear time.
Constructs a string initialized with the ASCII string str. The given const char pointer is converted to Unicode using the fromAscii() function.
You can disable this constructor by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.
Constructs a string initialized with the byte array ba. The given byte array is converted to Unicode using fromAscii(). Stops copying at the first 0 character, otherwise copies the entire byte array.
You can disable this constructor by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.
The append() function is typically very fast (constant time), because QString preallocates extra space at the end of the string data so it can grow without reallocating the entire string each time.
Appends the byte array ba to this string. The given byte array is converted to Unicode using the fromAscii() function.
You can disable this function by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.
Appends the string str to this string. The given const char pointer is converted to Unicode using the fromAscii() function.
You can disable this function by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.
Returns a copy of this string with the lowest numbered place marker replaced by string a, i.e., %1, %2, ..., %99.
fieldWidth specifies the minimum amount of space that argument a shall occupy. If a requires less space than fieldWidth, it is padded to fieldWidth with character fillChar. A positive fieldWidth produces right-aligned text. A negative fieldWidth produces left-aligned text.
This example shows how we might create a status string for reporting progress while processing a list of files:
QString i; // current file's number
QString total; // number of files to process
QString fileName; // current file's name
QString status = QString("Processing file %1 of %2: %3")
.arg(i).arg(total).arg(fileName);
One advantage of using arg() over sprintf() is that the order of the numbered place markers can change, if the application's strings are translated into other languages, but each arg() will still replace the lowest numbered unreplaced place marker, no matter where it appears. Also, if place marker %i appears more than once in the string, the arg() replaces all of them.
If there is no unreplaced place marker remaining, a warning message is output and the result is undefined. Place marker numbers must be in the range 1 to 99.
This is the same as str.arg(a1).arg(a2), except that the strings a1 and a2 are replaced in one pass. This can make a difference if a1 contains e.g. %1:
This is the same as calling str.arg(a1).arg(a2).arg(a3).arg(a4).arg(a5).arg(a6)), except that the strings a1, a2, a3, a4, a5, and a6 are replaced in one pass.
This is the same as calling str.arg(a1).arg(a2).arg(a3).arg(a4).arg(a5).arg(a6).arg(a7), except that the strings a1, a2, a3, a4, a5, a6, and a7 are replaced in one pass.
This is the same as calling str.arg(a1).arg(a2).arg(a3).arg(a4).arg(a5).arg(a6).arg(a7).arg(a8), except that the strings a1, a2, a3, a4, a5, a6, a7, and a8 are replaced in one pass.
This is the same as calling str.arg(a1).arg(a2).arg(a3).arg(a4).arg(a5).arg(a6).arg(a7).arg(a8).arg(a9), except that the strings a1, a2, a3, a4, a5, a6, a7, a8, and a9 are replaced in one pass.
QString QString::arg ( int a, int fieldWidth = 0, int base = 10, const QChar & fillChar = QLatin1Char( ' ' ) ) const
The a argument is expressed in base base, which is 10 by default and must be between 2 and 36. For bases other than 10, a is treated as an unsigned integer.
fieldWidth specifies the minimum amount of space that a is padded to and filled with the character fillChar. A positive value produces right-aligned text; a negative value produces left-aligned text.
The '%' can be followed by an 'L', in which case the sequence is replaced with a localized representation of a. The conversion uses the default locale, set by QLocale::setDefault(). If no default locale was specified, the "C" locale is used. The 'L' flag is ignored if base is not 10.
QString str;
str = QString("Decimal 63 is %1 in hexadecimal")
.arg(63, 0, 16);
// str == "Decimal 63 is 3f in hexadecimal"
QLocale::setDefault(QLocale(QLocale::English, QLocale::UnitedStates));
str = QString("%1 %L2 %L3")
.arg(12345)
.arg(12345)
.arg(12345, 0, 16);
// str == "12345 12,345 3039"
If fillChar is '0' (the number 0, ASCII 48), the locale's zero is used. For negative numbers, zero padding might appear before the minus sign.
QString QString::arg ( uinta, int fieldWidth = 0, int base = 10, const QChar & fillChar = QLatin1Char( ' ' ) ) const
fieldWidth specifies the minimum amount of space that a is padded to and filled with the character fillChar. A positive value produces right-aligned text; a negative value produces left-aligned text.
The a argument is expressed in the given base, which is 10 by default and must be between 2 and 36.
The '%' can be followed by an 'L', in which case the sequence is replaced with a localized representation of a. The conversion uses the default locale. The default locale is determined from the system's locale settings at application startup. It can be changed using QLocale::setDefault(). The 'L' flag is ignored if base is not 10.
QString str;
str = QString("Decimal 63 is %1 in hexadecimal")
.arg(63, 0, 16);
// str == "Decimal 63 is 3f in hexadecimal"
QLocale::setDefault(QLocale(QLocale::English, QLocale::UnitedStates));
str = QString("%1 %L2 %L3")
.arg(12345)
.arg(12345)
.arg(12345, 0, 16);
// str == "12345 12,345 3039"
If fillChar is '0' (the number 0, ASCII 48), the locale's zero is used. For negative numbers, zero padding might appear before the minus sign.
QString QString::arg ( ulonga, int fieldWidth = 0, int base = 10, const QChar & fillChar = QLatin1Char( ' ' ) ) const
fieldWidth specifies the minimum amount of space that a is padded to and filled with the character fillChar. A positive value produces right-aligned text; a negative value produces left-aligned text.
The base argument specifies the base to use when converting the integer a to a string. The base must be between 2 and 36, with 8 giving octal, 10 decimal, and 16 hexadecimal numbers.
If fillChar is '0' (the number 0, ASCII 48), the locale's zero is used. For negative numbers, zero padding might appear before the minus sign.
QString QString::arg ( qlonglonga, int fieldWidth = 0, int base = 10, const QChar & fillChar = QLatin1Char( ' ' ) ) const
fieldWidth specifies the minimum amount of space that a is padded to and filled with the character fillChar. A positive value produces right-aligned text; a negative value produces left-aligned text.
The base argument specifies the base to use when converting the integer a into a string. The base must be between 2 and 36, with 8 giving octal, 10 decimal, and 16 hexadecimal numbers.
If fillChar is '0' (the number 0, ASCII 48), the locale's zero is used. For negative numbers, zero padding might appear before the minus sign.
QString QString::arg ( qulonglonga, int fieldWidth = 0, int base = 10, const QChar & fillChar = QLatin1Char( ' ' ) ) const
fieldWidth specifies the minimum amount of space that a is padded to and filled with the character fillChar. A positive value produces right-aligned text; a negative value produces left-aligned text.
The base argument specifies the base to use when converting the integer a into a string. base must be between 2 and 36, with 8 giving octal, 10 decimal, and 16 hexadecimal numbers.
If fillChar is '0' (the number 0, ASCII 48), the locale's zero is used. For negative numbers, zero padding might appear before the minus sign.
QString QString::arg ( short a, int fieldWidth = 0, int base = 10, const QChar & fillChar = QLatin1Char( ' ' ) ) const
fieldWidth specifies the minimum amount of space that a is padded to and filled with the character fillChar. A positive value produces right-aligned text; a negative value produces left-aligned text.
The base argument specifies the base to use when converting the integer a into a string. The base must be between 2 and 36, with 8 giving octal, 10 decimal, and 16 hexadecimal numbers.
If fillChar is '0' (the number 0, ASCII 48), the locale's zero is used. For negative numbers, zero padding might appear before the minus sign.
QString QString::arg ( ushorta, int fieldWidth = 0, int base = 10, const QChar & fillChar = QLatin1Char( ' ' ) ) const
fieldWidth specifies the minimum amount of space that a is padded to and filled with the character fillChar. A positive value produces right-aligned text; a negative value produces left-aligned text.
The base argument specifies the base to use when converting the integer a into a string. The base must be between 2 and 36, with 8 giving octal, 10 decimal, and 16 hexadecimal numbers.
If fillChar is '0' (the number 0, ASCII 48), the locale's zero is used. For negative numbers, zero padding might appear before the minus sign.
Argument a is formatted according to the specified format and precision. See Argument Formats for details.
fieldWidth specifies the minimum amount of space that a is padded to and filled with the character fillChar. A positive value produces right-aligned text; a negative value produces left-aligned text.
The '%' can be followed by an 'L', in which case the sequence is replaced with a localized representation of a. The conversion uses the default locale, set by QLocale::setDefaultLocale(). If no default locale was specified, the "C" locale is used.
If fillChar is '0' (the number 0, ASCII 48), this function will use the locale's zero to pad. For negative numbers, the zero padding will probably appear before the minus sign.
Returns the maximum number of characters that can be stored in the string without forcing a reallocation.
The sole purpose of this function is to provide a means of fine tuning QString's memory usage. In general, you will rarely ever need to call this function. If you want to know how many characters are in the string, call size().
Compares s1 with s2 and returns an integer less than, equal to, or greater than zero if s1 is less than, equal to, or greater than s2.
If cs is Qt::CaseSensitive, the comparison is case sensitive; otherwise the comparison is case insensitive.
Case sensitive comparison is based exclusively on the numeric Unicode values of the characters and is very fast, but is not what a human would expect. Consider sorting user-visible strings with localeAwareCompare().
int x = QString::compare("aUtO", "AuTo", Qt::CaseInsensitive); // x == 0
int y = QString::compare("auto", "Car", Qt::CaseSensitive); // y > 0
int z = QString::compare("auto", "Car", Qt::CaseInsensitive); // z < 0
Lexically compares this string with the other string and returns an integer less than, equal to, or greater than zero if this string is less than, equal to, or greater than the other string.
Compares the string reference, ref, with the string and returns an integer less than, equal to, or greater than zero if the string is less than, equal to, or greater than ref.
Returns a pointer to the data stored in the QString. The pointer can be used to access the characters that compose the string. For convenience, the data is '\0'-terminated.
Note that the pointer remains valid only as long as the string is not modified.
Returns a pointer to the data stored in the QString. The pointer can be used to access and modify the characters that compose the string. For convenience, the data is '\0'-terminated.
Note that the pointer remains valid only as long as the string is not modified by other means. For read-only access, constData() is faster because it never causes a deep copy to occur.
Constructs a QString that uses the first size Unicode characters in the array unicode. The data in unicode is not copied. The caller must be able to guarantee that unicode will not be deleted or modified as long as the QString (or an unmodified copy of it) exists.
Any attempts to modify the QString or copies of it will cause it to create a deep copy of the data, ensuring that the raw data isn't modified.
Here's an example of how we can use a QRegExp on raw data in memory without requiring to copy the data into a QString:
Warning: A string created with fromRawData() is not '\0'-terminated, unless the raw data contains a '\0' character at position size. This means unicode() will not return a '\0'-terminated string (although utf16() does, at the cost of copying the raw data).
Returns a copy of the str string. The given string is assumed to be encoded in utf16 if the size of wchar_t is 2 bytes (e.g. on windows) and ucs4 if the size of wchar_t is 4 bytes (most Unix systems).
This method is only available if Qt is configured with STL compatibility enabled.
Returns a copy of the string, where the encoding of string depends on the size of wchar. If wchar is 4 bytes, the string is interpreted as ucs-4, if wchar is 2 bytes it is interpreted as ucs-2.
If size is -1 (default), the string has to be 0 terminated.
int QString::indexOf ( const QString & str, int from = 0, Qt::CaseSensitivitycs = Qt::CaseSensitive ) const
Returns the index position of the first occurrence of the string str in this string, searching forward from index position from. Returns -1 if str is not found.
If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.
Returns the index position of the first occurrence of the string str in this string, searching forward from index position from. Returns -1 if str is not found.
If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.
Returns the index position of the first occurrence of the character ch in the string, searching forward from index position from. Returns -1 if ch could not be found.
int QString::indexOf ( const QRegExp & rx, int from = 0 ) const
Returns the index position of the first match of the regular expression rx in the string, searching forward from index position from. Returns -1 if rx didn't match anywhere.
Example:
QString str = "the minimum";
str.indexOf(QRegExp("m[aeiou]"), 0); // returns 4
int QString::indexOf ( QRegExp & rx, int from = 0 ) const
Returns the index position of the first match of the regular expression rx in the string, searching forward from index position from. Returns -1 if rx didn't match anywhere.
If there is a match, the rx regular expression will contain the matched captures (see QRegExp::matchedLength, QRegExp::cap).
Example:
QString str = "the minimum";
str.indexOf(QRegExp("m[aeiou]"), 0); // returns 4
Qt makes a distinction between null strings and empty strings for historical reasons. For most applications, what matters is whether or not a string contains any data, and this can be determined using the isEmpty() function.
int QString::lastIndexOf ( const QString & str, int from = -1, Qt::CaseSensitivitycs = Qt::CaseSensitive ) const
Returns the index position of the last occurrence of the string str in this string, searching backward from index position from. If from is -1 (default), the search starts at the last character; if from is -2, at the next to last character and so on. Returns -1 if str is not found.
If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.
Returns the index position of the last occurrence of the string str in this string, searching backward from index position from. If from is -1 (default), the search starts at the last character; if from is -2, at the next to last character and so on. Returns -1 if str is not found.
If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.
Returns the index position of the last match of the regular expression rx in the string, searching backward from index position from. Returns -1 if rx didn't match anywhere.
Example:
QString str = "the minimum";
str.lastIndexOf(QRegExp("m[aeiou]")); // returns 8
int QString::lastIndexOf ( QRegExp & rx, int from = -1 ) const
Returns the index position of the last match of the regular expression rx in the string, searching backward from index position from. Returns -1 if rx didn't match anywhere.
If there is a match, the rx regular expression will contain the matched captures (see QRegExp::matchedLength, QRegExp::cap).
Example:
QString str = "the minimum";
str.lastIndexOf(QRegExp("m[aeiou]")); // returns 8
This function was introduced in Qt 4.5.
QString QString::left ( int n ) const
Returns a substring that contains the n leftmost characters of the string.
The entire string is returned if n is greater than size() or less than zero.
QString x = "Pineapple";
QString y = x.left(4); // y == "Pine"
Returns a string of size width that contains this string padded by the fill character.
If truncate is false and the size() of the string is more than width, then the returned string is a copy of the string.
QString s = "apple";
QString t = s.leftJustified(8, '.'); // t == "apple..."
If truncate is true and the size() of the string is more than width, then any characters in a copy of the string after position width are removed, and the copy is returned.
Compares this string with the other string and returns an integer less than, equal to, or greater than zero if this string is less than, equal to, or greater than the other string.
The comparison is performed in a locale- and also platform-dependent manner. Use this function to present sorted lists of strings to the user.
Compares this string with the other string and returns an integer less than, equal to, or greater than zero if this string is less than, equal to, or greater than the other string.
The comparison is performed in a locale- and also platform-dependent manner. Use this function to present sorted lists of strings to the user.
Same as localeAwareCompare(*this, other).
QString QString::mid ( int position, int n = -1 ) const
Returns a string that contains n characters of this string, starting at the specified position index.
Returns a null string if the position index exceeds the length of the string. If there are less than n characters available in the string starting at the given position, or if n is -1 (default), the function returns all characters that are available from the specified position.
Example:
QString x = "Nine pineapples";
QString y = x.mid(5, 4); // y == "pine"
QString z = x.mid(5); // z == "pineapples"
QStringRef QString::midRef ( int position, int n = -1 ) const
Returns a substring reference to n characters of this string, starting at the specified position.
If the position exceeds the length of the string, an empty reference is returned.
If there are less than n characters available in the string, starting at the given position, or if n is -1 (default), the function returns all characters from the specified position onwards.
Example:
QString x = "Nine pineapples";
QStringRef y = x.midRef(5, 4); // y == "pine"
QStringRef z = x.midRef(5); // z == "pineapples"
Prepends the byte array ba to this string. The byte array is converted to Unicode using the fromAscii() function.
You can disable this function by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.
Prepends the string str to this string. The const char pointer is converted to Unicode using the fromAscii() function.
You can disable this function by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.
Appends the given ch character onto the end of this string.
void QString::push_front ( const QString & other )
This function is provided for STL compatibility, prepending the given other string to the beginning of this string. It is equivalent to prepend(other).
Prepends the given ch character to the beginning of this string.
QString & QString::remove ( int position, int n )
Removes n characters from the string, starting at the given position index, and returns a reference to the string.
If the specified position index is within the string, but position + n is beyond the end of the string, the string is truncated at the specified position.
QString s = "Montreal";
s.remove(1, 4);
// s == "Meal"
Replaces each occurrence in this string of the first blen characters of before with the first alen characters of after and returns a reference to this string.
If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.
Attempts to allocate memory for at least size characters. If you know in advance how large the string will be, you can call this function, and if you resize the string often you are likely to get better performance. If size is an underestimate, the worst that will happen is that the QString will be a bit slower.
The sole purpose of this function is to provide a means of fine tuning QString's memory usage. In general, you will rarely ever need to call this function. If you want to change the size of the string, call resize().
This function is useful for code that needs to build up a long string and wants to avoid repeated reallocation. In this example, we want to add to the string until some condition is true, and we're fairly sure that size is large enough to make a call to reserve() worthwhile:
QString result;
int maxSize;
bool condition;
QChar nextChar;
result.reserve(maxSize);
while (condition)
result.append(nextChar);
result.squeeze();
If size is greater than the current size, the string is extended to make it size characters long with the extra characters added to the end. The new characters are uninitialized.
If size is less than the current size, characters are removed from the end.
Example:
QString s = "Hello world";
s.resize(5);
// s == "Hello"
s.resize(8);
// s == "Hello???" (where ? stands for any character)
If you want to append a certain number of identical characters to the string, use operator+=() as follows rather than resize():
QString t = "Hello";
t += QString(10, 'X');
// t == "HelloXXXXXXXXXX"
If you want to expand the string so that it reaches a certain width and fill the new positions with a particular character, use the leftJustified() function:
If size is negative, it is equivalent to passing zero.
QString r = "Hello";
r = r.leftJustified(10, ' ');
// r == "Hello "
QString QString::section ( QCharsep, int start, int end = -1, SectionFlagsflags = SectionDefault ) const
This function returns a section of the string.
This string is treated as a sequence of fields separated by the character, sep. The returned string consists of the fields from position start to position end inclusive. If end is not specified, all fields from position start to the end of the string are included. Fields are numbered 0, 1, 2, etc., counting from the left, and -1, -2, etc., counting from right to left.
The flags argument can be used to affect some aspects of the function's behavior, e.g. whether to be case sensitive, whether to skip empty fields and how to deal with leading and trailing separators; see SectionFlags.
If start or end is negative, we count fields from the right of the string, the right-most field being -1, the one from right-most field being -2, and so on.
QString & QString::setNum ( int n, int base = 10 )
Sets the string to the printed value of n in the specified base, and returns a reference to the string.
The base is 10 by default and must be between 2 and 36. For bases other than 10, n is treated as an unsigned integer.
QString str;
str.setNum(1234); // str == "1234"
The formatting always uses QLocale::C, i.e., English/UnitedStates. To get a localized string representation of a number, use QLocale::toString() with the appropriate locale.
QString & QString::setNum ( uintn, int base = 10 )
This is an overloaded function.
QString & QString::setNum ( long n, int base = 10 )
This is an overloaded function.
QString & QString::setNum ( ulongn, int base = 10 )
This is an overloaded function.
QString & QString::setNum ( qlonglongn, int base = 10 )
This is an overloaded function.
QString & QString::setNum ( qulonglongn, int base = 10 )
This is an overloaded function.
QString & QString::setNum ( short n, int base = 10 )
This is an overloaded function.
QString & QString::setNum ( ushortn, int base = 10 )
This is an overloaded function.
QString & QString::setNum ( double n, char format = 'g', int precision = 6 )
This is an overloaded function.
Sets the string to the printed value of n, formatted according to the given format and precision, and returns a reference to the string.
The format can be 'f', 'F', 'e', 'E', 'g' or 'G' (see the arg() function documentation for an explanation of the formats).
Unlike QLocale::toString(), this function doesn't honor the user's locale settings.
QString & QString::setNum ( float n, char format = 'g', int precision = 6 )
This is an overloaded function.
Sets the string to the printed value of n, formatted according to the given format and precision, and returns a reference to the string.
Returns a string that has whitespace removed from the start and the end, and that has each sequence of internal whitespace replaced with a single space.
Whitespace means any character for which QChar::isSpace() returns true. This includes the ASCII characters '\t', '\n', '\v', '\f', '\r', and ' '.
The last character in the string is at position size() - 1. In addition, QString ensures that the character at position size() is always '\0', so that you can use the return value of data() and constData() as arguments to functions that expect '\0'-terminated strings.
Example:
QString str = "World";
int n = str.size(); // n == 5
str.data()[0]; // returns 'W'
str.data()[4]; // returns 'd'
str.data()[5]; // returns '\0'
Splits the string into substrings wherever sep occurs, and returns the list of those strings. If sep does not match anywhere in the string, split() returns a single-element list containing this string.
cs specifies whether sep should be matched case sensitively or case insensitively.
If behavior is QString::SkipEmptyParts, empty entries don't appear in the result. By default, empty entries are kept.
Splits the string into substrings wherever the regular expression rx matches, and returns the list of those strings. If rx does not match anywhere in the string, split() returns a single-element list containing this string.
Here's an example where we extract the words in a sentence using one or more whitespace characters as the separator:
Here's a similar example, but this time we use any sequence of non-word characters as the separator:
str = "This time, a normal English sentence.";
list = str.split(QRegExp("\\W+"), QString::SkipEmptyParts);
// list: [ "This", "time", "a", "normal", "English", "sentence" ]
Here's a third example where we use a zero-length assertion, \b (word boundary), to split the string into an alternating sequence of non-word and word tokens:
Safely builds a formatted string from the format string cformat and an arbitrary list of arguments.
The %lc escape sequence expects a unicode character of type ushort (as returned by QChar::unicode()). The %ls escape sequence expects a pointer to a zero-terminated array of unicode characters of type ushort (as returned by QString::utf16()).
Note: This function expects a UTF-8 string for %s and Latin-1 for the format string.
The format string supports most of the conversion specifiers provided by printf() in the standard C++ library. It doesn't honor the length modifiers (e.g. h for short, ll for long long). If you need those, use the standard snprintf() function instead:
Warning: We do not recommend using QString::sprintf() in new Qt code. Instead, consider using QTextStream or arg(), both of which support Unicode strings seamlessly and are type-safe. Here's an example that uses QTextStream:
For translations, especially if the strings contains more than one escape sequence, you should consider using the arg() function instead. This allows the order of the replacements to be controlled by the translator.
Releases any memory not required to store the character data.
The sole purpose of this function is to provide a means of fine tuning QString's memory usage. In general, you will rarely ever need to call this function.
Returns an 8-bit ASCII representation of the string as a QByteArray.
If a codec has been set using QTextCodec::setCodecForCStrings(), it is used to convert Unicode to 8-bit char; otherwise this function does the same as toLatin1().
Returns the case folded equivalent of the string. For most Unicode characters this is the same as toLower().
double QString::toDouble ( bool * ok = 0 ) const
Returns the string converted to a double value.
Returns 0.0 if the conversion fails.
If a conversion error occurs, *ok is set to false; otherwise *ok is set to true.
QString str = "1234.56";
double val = str.toDouble(); // val == 1234.56
Various string formats for floating point numbers can be converted to double values:
bool ok;
double d;
d = QString( "1234.56e-02" ).toDouble(&ok); // ok == true, d == 12.3456
This function tries to interpret the string according to the current locale. The current locale is determined from the system at application startup and can be changed by calling QLocale::setDefault(). If the string cannot be interpreted according to the current locale, this function falls back on the "C" locale.
QLocale::setDefault(QLocale::C);
d = QString( "1234,56" ).toDouble(&ok); // ok == false
d = QString( "1234.56" ).toDouble(&ok); // ok == true, d == 1234.56
QLocale::setDefault(QLocale::German);
d = QString( "1234,56" ).toDouble(&ok); // ok == true, d == 1234.56
d = QString( "1234.56" ).toDouble(&ok); // ok == true, d == 1234.56
Due to the ambiguity between the decimal point and thousands group separator in various locales, this function does not handle thousands group separators. If you need to convert such numbers, see QLocale::toDouble().
QLocale::setDefault(QLocale::C);
d = QString( "1234,56" ).toDouble(&ok); // ok == false
int QString::toInt ( bool * ok = 0, int base = 10 ) const
Returns the string converted to an int using base base, which is 10 by default and must be between 2 and 36, or 0. Returns 0 if the conversion fails.
If a conversion error occurs, *ok is set to false; otherwise *ok is set to true.
If base is 0, the C language convention is used: If the string begins with "0x", base 16 is used; if the string begins with "0", base 8 is used; otherwise, base 10 is used.
Example:
QString str = "FF";
bool ok;
int hex = str.toInt(&ok, 16); // hex == 255, ok == true
int dec = str.toInt(&ok, 10); // dec == 0, ok == false
Returns the local 8-bit representation of the string as a QByteArray. The returned byte array is undefined if the string contains characters not supported by the local 8-bit encoding.
long QString::toLong ( bool * ok = 0, int base = 10 ) const
Returns the string converted to a long using base base, which is 10 by default and must be between 2 and 36, or 0. Returns 0 if the conversion fails.
If a conversion error occurs, *ok is set to false; otherwise *ok is set to true.
If base is 0, the C language convention is used: If the string begins with "0x", base 16 is used; if the string begins with "0", base 8 is used; otherwise, base 10 is used.
Example:
QString str = "FF";
bool ok;
long hex = str.toLong(&ok, 16); // hex == 255, ok == true
long dec = str.toLong(&ok, 10); // dec == 0, ok == false
qlonglong QString::toLongLong ( bool * ok = 0, int base = 10 ) const
Returns the string converted to a long long using base base, which is 10 by default and must be between 2 and 36, or 0. Returns 0 if the conversion fails.
If a conversion error occurs, *ok is set to false; otherwise *ok is set to true.
If base is 0, the C language convention is used: If the string begins with "0x", base 16 is used; if the string begins with "0", base 8 is used; otherwise, base 10 is used.
Example:
QString str = "FF";
bool ok;
qint64 hex = str.toLongLong(&ok, 16); // hex == 255, ok == true
qint64 dec = str.toLongLong(&ok, 10); // dec == 0, ok == false
short QString::toShort ( bool * ok = 0, int base = 10 ) const
Returns the string converted to a short using base base, which is 10 by default and must be between 2 and 36, or 0. Returns 0 if the conversion fails.
If a conversion error occurs, *ok is set to false; otherwise *ok is set to true.
If base is 0, the C language convention is used: If the string begins with "0x", base 16 is used; if the string begins with "0", base 8 is used; otherwise, base 10 is used.
Example:
QString str = "FF";
bool ok;
short hex = str.toShort(&ok, 16); // hex == 255, ok == true
short dec = str.toShort(&ok, 10); // dec == 0, ok == false
Returns a std::string object with the data contained in this QString. The Unicode data is converted into 8-bit characters using the toAscii() function.
This operator is mostly useful to pass a QString to a function that accepts a std::string object.
If the QString contains non-ASCII Unicode characters, using this operator can lead to loss of information, since the implementation calls toAscii().
This operator is only available if Qt is configured with STL compatibility enabled.
Returns a std::wstring object with the data contained in this QString. The std::wstring is encoded in utf16 on platforms where wchar_t is 2 bytes wide (e.g. windows) and in ucs4 on platforms where wchar_t is 4 bytes wide (most Unix systems).
This operator is mostly useful to pass a QString to a function that accepts a std::wstring object.
This operator is only available if Qt is configured with STL compatibility enabled.
uint QString::toUInt ( bool * ok = 0, int base = 10 ) const
Returns the string converted to an unsigned int using base base, which is 10 by default and must be between 2 and 36, or 0. Returns 0 if the conversion fails.
If a conversion error occurs, *ok is set to false; otherwise *ok is set to true.
If base is 0, the C language convention is used: If the string begins with "0x", base 16 is used; if the string begins with "0", base 8 is used; otherwise, base 10 is used.
Example:
QString str = "FF";
bool ok;
uint hex = str.toUInt(&ok, 16); // hex == 255, ok == true
uint dec = str.toUInt(&ok, 10); // dec == 0, ok == false
ulong QString::toULong ( bool * ok = 0, int base = 10 ) const
Returns the string converted to an unsigned long using base base, which is 10 by default and must be between 2 and 36, or 0. Returns 0 if the conversion fails.
If a conversion error occurs, *ok is set to false; otherwise *ok is set to true.
If base is 0, the C language convention is used: If the string begins with "0x", base 16 is used; if the string begins with "0", base 8 is used; otherwise, base 10 is used.
Example:
QString str = "FF";
bool ok;
ulong hex = str.toULong(&ok, 16); // hex == 255, ok == true
ulong dec = str.toULong(&ok, 10); // dec == 0, ok == false
qulonglong QString::toULongLong ( bool * ok = 0, int base = 10 ) const
Returns the string converted to an unsigned long long using base base, which is 10 by default and must be between 2 and 36, or 0. Returns 0 if the conversion fails.
If a conversion error occurs, *ok is set to false; otherwise *ok is set to true.
If base is 0, the C language convention is used: If the string begins with "0x", base 16 is used; if the string begins with "0", base 8 is used; otherwise, base 10 is used.
Example:
QString str = "FF";
bool ok;
quint64 hex = str.toULongLong(&ok, 16); // hex == 255, ok == true
quint64 dec = str.toULongLong(&ok, 10); // dec == 0, ok == false
ushort QString::toUShort ( bool * ok = 0, int base = 10 ) const
Returns the string converted to an unsigned short using base base, which is 10 by default and must be between 2 and 36, or 0. Returns 0 if the conversion fails.
If a conversion error occurs, *ok is set to false; otherwise *ok is set to true.
If base is 0, the C language convention is used: If the string begins with "0x", base 16 is used; if the string begins with "0", base 8 is used; otherwise, base 10 is used.
Example:
QString str = "FF";
bool ok;
ushort hex = str.toUShort(&ok, 16); // hex == 255, ok == true
ushort dec = str.toUShort(&ok, 10); // dec == 0, ok == false
int QString::toWCharArray ( wchar_t * array ) const
Fills the array with the data contained in this QString object. The array is encoded in utf16 on platforms where wchar_t is 2 bytes wide (e.g. windows) and in ucs4 on platforms where wchar_t is 4 bytes wide (most Unix systems).
array has to be allocated by the caller and contain enough space to hold the complete string (allocating the array with the same length as the string is always sufficient).
returns the actual length of the string in array.
Note: This function does not append a null character to the array.
Equivalent method to sprintf(), but takes a va_list ap instead a list of variable arguments. See the sprintf() documentation for an explanation of cformat.
This method does not call the va_end macro, the caller is responsible to call va_end on ap.
bool QString::operator!= ( const QString & other ) const
Returns true if this string is not equal to string other; otherwise returns false.
The comparison is based exclusively on the numeric Unicode values of the characters and is very fast, but is not what a human would expect. Consider sorting user-interface strings with localeAwareCompare().
bool QString::operator!= ( const QLatin1String & other ) const
The other byte array is converted to a QString using the fromAscii() function.
You can disable this operator by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.
bool QString::operator!= ( const char * other ) const
The other const char pointer is converted to a QString using the fromAscii() function.
You can disable this operator by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.
QString & QString::operator+= ( const QString & other )
Appends the string other onto the end of this string and returns a reference to this string.
Example:
QString x = "free";
QString y = "dom";
x += y;
// x == "freedom"
This operation is typically very fast (constant time), because QString preallocates extra space at the end of the string data so it can grow without reallocating the entire string each time.
Appends the byte array ba to this string. The byte array is converted to Unicode using the fromAscii() function.
You can disable this function by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.
Appends the string str to this string. The const char pointer is converted to Unicode using the fromAscii() function.
You can disable this function by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.
Appends the character ch to this string. The character is converted to Unicode using the fromAscii() function.
You can disable this function by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.
bool QString::operator< ( const QString & other ) const
Returns true if this string is lexically less than string other; otherwise returns false.
The comparison is based exclusively on the numeric Unicode values of the characters and is very fast, but is not what a human would expect. Consider sorting user-interface strings using the QString::localeAwareCompare() function.
bool QString::operator< ( const QLatin1String & other ) const
The other byte array is converted to a QString using the fromAscii() function.
You can disable this operator by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.
bool QString::operator< ( const char * other ) const
The other const char pointer is converted to a QString using the fromAscii() function.
You can disable this operator by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.
bool QString::operator<= ( const QString & other ) const
Returns true if this string is lexically less than or equal to string other; otherwise returns false.
The comparison is based exclusively on the numeric Unicode values of the characters and is very fast, but is not what a human would expect. Consider sorting user-interface strings with localeAwareCompare().
bool QString::operator<= ( const QLatin1String & other ) const
The other byte array is converted to a QString using the fromAscii() function.
You can disable this operator by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.
bool QString::operator<= ( const char * other ) const
The other const char pointer is converted to a QString using the fromAscii() function.
You can disable this operator by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.
QString & QString::operator= ( const QString & other )
Assigns other to this string and returns a reference to this string.
Assigns ba to this string. The byte array is converted to Unicode using the fromAscii() function.
You can disable this operator by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.
Assigns str to this string. The const char pointer is converted to Unicode using the fromAscii() function.
You can disable this operator by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.
Assigns character ch to this string. The character is converted to Unicode using the fromAscii() function.
You can disable this operator by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.
Sets the string to contain the single character ch.
bool QString::operator== ( const QString & other ) const
Returns true if string other is equal to this string; otherwise returns false.
The comparison is based exclusively on the numeric Unicode values of the characters and is very fast, but is not what a human would expect. Consider sorting user-interface strings with localeAwareCompare().
bool QString::operator== ( const QLatin1String & other ) const
The other byte array is converted to a QString using the fromAscii() function.
You can disable this operator by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.
bool QString::operator== ( const char * other ) const
The other const char pointer is converted to a QString using the fromAscii() function.
You can disable this operator by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.
bool QString::operator> ( const QString & other ) const
Returns true if this string is lexically greater than string other; otherwise returns false.
The comparison is based exclusively on the numeric Unicode values of the characters and is very fast, but is not what a human would expect. Consider sorting user-interface strings with localeAwareCompare().
bool QString::operator> ( const QLatin1String & other ) const
The other byte array is converted to a QString using the fromAscii() function.
You can disable this operator by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.
bool QString::operator> ( const char * other ) const
The other const char pointer is converted to a QString using the fromAscii() function.
You can disable this operator by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.
bool QString::operator>= ( const QString & other ) const
Returns true if this string is lexically greater than or equal to string other; otherwise returns false.
The comparison is based exclusively on the numeric Unicode values of the characters and is very fast, but is not what a human would expect. Consider sorting user-interface strings with localeAwareCompare().
bool QString::operator>= ( const QLatin1String & other ) const
The other byte array is converted to a QString using the fromAscii() function.
You can disable this operator by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.
bool QString::operator>= ( const char * other ) const
The other const char pointer is converted to a QString using the fromAscii() function.
You can disable this operator by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.
QCharRef QString::operator[] ( int position )
Returns the character at the specified position in the string as a modifiable reference.
Example:
QString str;
if (str[0] == QChar('?'))
str[0] = QChar('_');
The return value is of type QCharRef, a helper class for QString. When you get an object of type QCharRef, you can use it as if it were a QChar &. If you assign to it, the assignment will apply to the character in the QString from which you got the reference.
Returns true if s1 is lexically less than s2; otherwise returns false. For s1 != 0, this is equivalent to compare(s1, s2) < 0.
The comparison is based exclusively on the numeric Unicode values of the characters and is very fast, but is not what a human would expect. Consider sorting user-interface strings using the QString::localeAwareCompare() function.
Returns true if s1 is lexically less than or equal to s2; otherwise returns false. For s1 != 0, this is equivalent to compare(s1, s2) <= 0.
The comparison is based exclusively on the numeric Unicode values of the characters and is very fast, but is not what a human would expect. Consider sorting user-interface strings with QString::localeAwareCompare().
Returns true if s1 is lexically greater than s2; otherwise returns false. Equivalent to compare(s1, s2) > 0.
The comparison is based exclusively on the numeric Unicode values of the characters and is very fast, but is not what a human would expect. Consider sorting user-interface strings using the QString::localeAwareCompare() function.
Returns true if s1 is lexically greater than or equal to s2; otherwise returns false. For s1 != 0, this is equivalent to compare(s1, s2) >= 0.
The comparison is based exclusively on the numeric Unicode values of the characters and is very fast, but is not what a human would expect. Consider sorting user-interface strings using the QString::localeAwareCompare() function.
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