QLatin1String Class▲
-
Header: QLatin1String
-
qmake: QT += core
-
Group: QLatin1String is part of string-processing
Detailed Description▲
Many of QString's member functions are overloaded to accept const char * instead of QString. This includes the copy constructor, the assignment operator, the comparison operators, and various other functions such as insert(), replace(), and indexOf(). These functions are usually optimized to avoid constructing a QString object for the const char * data. For example, assuming str is a QString,
if (str == "auto" || str == "extern"
|| str == "static" || str == "register") {
...
}is much faster than
if (str == QString("auto") || str == QString("extern")
|| str == QString("static") || str == QString("register")) {
...
}because it doesn't construct four temporary QString objects and make a deep copy of the character data.
Applications that define QT_NO_CAST_FROM_ASCII (as explained in the QString documentation) don't have access to QString's const char * API. To provide an efficient way of specifying constant Latin-1 strings, Qt provides the QLatin1String, which is just a very thin wrapper around a const char *. Using QLatin1String, the example code above becomes
if (str == QLatin1String("auto")
|| str == QLatin1String("extern")
|| str == QLatin1String("static")
|| str == QLatin1String("register") {
...
}This is a bit longer to type, but it provides exactly the same benefits as the first version of the code, and is faster than converting the Latin-1 strings using QString::fromLatin1().
Thanks to the QString(QLatin1String) constructor, QLatin1String can be used everywhere a QString is expected. For example:
QLabel *label = new QLabel(QLatin1String("MOD"), this);If the function you're calling with a QLatin1String argument isn't actually overloaded to take QLatin1String, the implicit conversion to QString will trigger a memory allocation, which is usually what you want to avoid by using QLatin1String in the first place. In those cases, using QStringLiteral may be the better option.
See Also▲
See also QString, QLatin1Char, QStringLiteral, QT_NO_CAST_FROM_ASCII
Member Type Documentation▲
[alias, since 5.10] QLatin1String::const_iterator▲
This typedef provides an STL-style const iterator for QLatin1String.
This typedef was introduced in Qt 5.10.
See Also▲
See also iterator, const_reverse_iterator
[alias, since 5.11] QLatin1String::const_reference▲
Alias for reference. Provided for compatibility with the STL.
This typedef was introduced in Qt 5.11.
[alias, since 5.10] QLatin1String::const_reverse_iterator▲
This typedef provides an STL-style const reverse iterator for QLatin1String.
This typedef was introduced in Qt 5.10.
See Also▲
See also reverse_iterator, const_iterator
[alias, since 5.10] QLatin1String::difference_type▲
Alias for int. Provided for compatibility with the STL.
This typedef was introduced in Qt 5.10.
[alias, since 5.10] QLatin1String::iterator▲
This typedef provides an STL-style const iterator for QLatin1String.
QLatin1String does not support mutable iterators, so this is the same as const_iterator.
This typedef was introduced in Qt 5.10.
See Also▲
See also const_iterator, reverse_iterator
[alias, since 5.10] QLatin1String::reference▲
Alias for value_type &. Provided for compatibility with the STL.
This typedef was introduced in Qt 5.10.
[alias, since 5.10] QLatin1String::reverse_iterator▲
This typedef provides an STL-style const reverse iterator for QLatin1String.
QLatin1String does not support mutable reverse iterators, so this is the same as const_reverse_iterator.
This typedef was introduced in Qt 5.10.
See Also▲
See also const_reverse_iterator, iterator
[alias, since 5.10] QLatin1String::size_type▲
Alias for int. Provided for compatibility with the STL.
This typedef was introduced in Qt 5.10.
[alias, since 5.10] QLatin1String::value_type▲
Alias for const char. Provided for compatibility with the STL.
This typedef was introduced in Qt 5.10.
Member Function Documentation▲
[since 5.10] bool QLatin1String::startsWith(QChar ch) const▲
[since 5.10] bool QLatin1String::startsWith(QChar ch, Qt::CaseSensitivity cs) const
[since 5.10] bool QLatin1String::startsWith(QLatin1String l1, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
[since 5.10] bool QLatin1String::startsWith(QStringView str, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
Returns true if this Latin-1 string starts with string-view str, Latin-1 string l1, or character ch, respectively; otherwise returns false.
If cs is Qt::CaseSensitive (the default), the search is case-sensitive; otherwise the search is case-insensitive.
This function was introduced in Qt 5.10.
See Also▲
See also endsWith()
[since 5.10] bool QLatin1String::endsWith(QChar ch) const▲
[since 5.10] bool QLatin1String::endsWith(QChar ch, Qt::CaseSensitivity cs) const
[since 5.10] bool QLatin1String::endsWith(QLatin1String l1, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
[since 5.10] bool QLatin1String::endsWith(QStringView str, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
Returns true if this Latin-1 string ends with string-view str, Latin-1 string l1, or character ch, respectively; otherwise returns false.
If cs is Qt::CaseSensitive (the default), the search is case-sensitive; otherwise the search is case-insensitive.
This function was introduced in Qt 5.10.
See Also▲
See also startsWith()
[since 5.6] QLatin1String::QLatin1String()▲
Constructs a QLatin1String object that stores a nullptr.
This function was introduced in Qt 5.6.
QLatin1String::QLatin1String(const char *str)▲
Constructs a QLatin1String object that stores str.
The string data is not copied. The caller must be able to guarantee that str will not be deleted or modified as long as the QLatin1String object exists.
See Also▲
See also latin1()
[since 5.10] QLatin1String::QLatin1String(const char *first, const char *last)▲
Constructs a QLatin1String object that stores first with length (last - first).
The range [first,last) must remain valid for the lifetime of this Latin-1 string object.
Passing nullptr as first is safe if last is nullptr, too, and results in a null Latin-1 string.
The behavior is undefined if last precedes first, first is nullptr and last is not, or if last - first > INT_MAX.
This function was introduced in Qt 5.10.
QLatin1String::QLatin1String(const char *str, int size)▲
Constructs a QLatin1String object that stores str with size.
The string data is not copied. The caller must be able to guarantee that str will not be deleted or modified as long as the QLatin1String object exists.
See Also▲
See also latin1()
[explicit] QLatin1String::QLatin1String(const QByteArray &str)▲
Constructs a QLatin1String object that stores str.
The string data is not copied. The caller must be able to guarantee that str will not be deleted or modified as long as the QLatin1String object exists.
See Also▲
See also latin1()
[since 5.8] QLatin1Char QLatin1String::at(int pos) const▲
Returns the character at position pos in this object.
This function performs no error checking. The behavior is undefined when pos < 0 or pos >= size().
This function was introduced in Qt 5.8.
See Also▲
See also operator[]()
[since 5.10] QLatin1Char QLatin1String::back() const▲
Returns the last character in the string. Same as at(size() - 1).
This function is provided for STL compatibility.
Calling this function on an empty string constitutes undefined behavior.
This function was introduced in Qt 5.10.
See Also▲
See also front(), at(), operator[]()
[since 5.10] QLatin1String::const_iterator QLatin1String::begin() const▲
Returns a const STL-style iterator pointing to the first character in the string.
This function is provided for STL compatibility.
This function was introduced in Qt 5.10.
See Also▲
[since 5.10] QLatin1String::const_iterator QLatin1String::cbegin() const▲
Same as begin().
This function is provided for STL compatibility.
This function was introduced in Qt 5.10.
See Also▲
[since 5.10] QLatin1String::const_iterator QLatin1String::cend() const▲
Same as end().
This function is provided for STL compatibility.
This function was introduced in Qt 5.10.
See Also▲
[since 5.10] void QLatin1String::chop(int length)▲
Truncates this string by length characters.
Same as *this = left(size() - length).
The behavior is undefined when length < 0 or length > size().
This function was introduced in Qt 5.10.
See Also▲
[since 5.10] QLatin1String QLatin1String::chopped(int length) const▲
Returns the substring of length size() - length starting at the beginning of this object.
Same as left(size() - length).
The behavior is undefined when length < 0 or length > size().
This function was introduced in Qt 5.10.
See Also▲
[since 5.10] QLatin1String::const_reverse_iterator QLatin1String::crbegin() const▲
Same as rbegin().
This function is provided for STL compatibility.
This function was introduced in Qt 5.10.
See Also▲
[since 5.10] QLatin1String::const_reverse_iterator QLatin1String::crend() const▲
Same as rend().
This function is provided for STL compatibility.
This function was introduced in Qt 5.10.
See Also▲
const char *QLatin1String::data() const▲
Returns the Latin-1 string stored in this object.
[since 5.10] QLatin1String::const_iterator QLatin1String::end() const▲
Returns a const STL-style iterator pointing to the imaginary character after the last character in the list.
This function is provided for STL compatibility.
This function was introduced in Qt 5.10.
See Also▲
[since 5.10] QLatin1Char QLatin1String::front() const▲
Returns the first character in the string. Same as at(0).
This function is provided for STL compatibility.
Calling this function on an empty string constitutes undefined behavior.
This function was introduced in Qt 5.10.
See Also▲
See also back(), at(), operator[]()
[since 5.10] bool QLatin1String::isEmpty() const▲
Returns whether the Latin-1 string stored in this object is empty (size() == 0) or not.
This function was introduced in Qt 5.10.
See Also▲
[since 5.10] bool QLatin1String::isNull() const▲
Returns whether the Latin-1 string stored in this object is null (data() == nullptr) or not.
This function was introduced in Qt 5.10.
See Also▲
const char *QLatin1String::latin1() const▲
Returns the Latin-1 string stored in this object.
[since 5.8] QLatin1String QLatin1String::left(int length) const▲
Returns the substring of length length starting at position 0 in this object.
This function performs no error checking. The behavior is undefined when length < 0 or length > size().
This function was introduced in Qt 5.8.
See Also▲
[since 5.8] QLatin1String QLatin1String::mid(int start) const▲
Returns the substring starting at position start in this object, and extending to the end of the string.
This function performs no error checking. The behavior is undefined when start < 0 or start > size().
This function was introduced in Qt 5.8.
See Also▲
[since 5.8] QLatin1String QLatin1String::mid(int start, int length) const▲
This is an overloaded function.
Returns the substring of length length starting at position start in this object.
This function performs no error checking. The behavior is undefined when start < 0, length < 0, or start + length > size().
This function was introduced in Qt 5.8.
See Also▲
[since 5.10] QLatin1String::const_reverse_iterator QLatin1String::rbegin() const▲
Returns a const STL-style reverse iterator pointing to the first character in the string, in reverse order.
This function is provided for STL compatibility.
This function was introduced in Qt 5.10.
See Also▲
[since 5.10] QLatin1String::const_reverse_iterator QLatin1String::rend() const▲
Returns a STL-style reverse iterator pointing to one past the last character in the string, in reverse order.
This function is provided for STL compatibility.
This function was introduced in Qt 5.10.
See Also▲
[since 5.8] QLatin1String QLatin1String::right(int length) const▲
Returns the substring of length length starting at position size() - length in this object.
This function performs no error checking. The behavior is undefined when length < 0 or length > size().
This function was introduced in Qt 5.8.
See Also▲
int QLatin1String::size() const▲
Returns the size of the Latin-1 string stored in this object.
[since 5.10] QLatin1String QLatin1String::trimmed() const▲
Strips leading and trailing whitespace and returns the result.
Whitespace means any character for which QChar::isSpace() returns true. This includes the ASCII characters '\t', '\n', '\v', '\f', '\r', and ' '.
This function was introduced in Qt 5.10.
[since 5.10] void QLatin1String::truncate(int length)▲
Truncates this string to length length.
Same as *this = left(length).
The behavior is undefined when length < 0 or length > size().
This function was introduced in Qt 5.10.
See Also▲
bool QLatin1String::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 QString::localeAwareCompare().
[since 4.3] bool QLatin1String::operator!=(const char *other) const▲
This function overloads operator!=().
The other const char pointer is converted to a QString using the QString::fromUtf8() 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.
This function was introduced in Qt 4.3.
See Also▲
See also QT_NO_CAST_FROM_ASCII
[since 5.0] bool QLatin1String::operator!=(const QByteArray &other) const▲
This function overloads operator!=().
The other byte array is converted to a QString using the QString::fromUtf8() 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.
This function was introduced in Qt 5.0.
See Also▲
See also QT_NO_CAST_FROM_ASCII
bool QLatin1String::operator<(const QString &other) const▲
Returns true if this string is lexically less than the other 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 using the QString::localeAwareCompare() function.
[since 4.3] bool QLatin1String::operator<(const char *other) const▲
This is an overloaded function.
The other const char pointer is converted to a QString using the QString::fromUtf8() 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.
This function was introduced in Qt 4.3.
See Also▲
See also QT_NO_CAST_FROM_ASCII
[since 5.0] bool QLatin1String::operator<(const QByteArray &other) const▲
This is an overloaded function.
The other const char pointer is converted to a QString using the QString::fromUtf8() 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.
This function was introduced in Qt 5.0.
See Also▲
See also QT_NO_CAST_FROM_ASCII
bool QLatin1String::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 QString::localeAwareCompare().
[since 4.3] bool QLatin1String::operator<=(const char *other) const▲
This is an overloaded function.
The other const char pointer is converted to a QString using the QString::fromUtf8() 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.
This function was introduced in Qt 4.3.
See Also▲
See also QT_NO_CAST_FROM_ASCII
[since 5.0] bool QLatin1String::operator<=(const QByteArray &other) const▲
This is an overloaded function.
The other array is converted to a QString using the QString::fromUtf8() 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.
This function was introduced in Qt 5.0.
See Also▲
See also QT_NO_CAST_FROM_ASCII
bool QLatin1String::operator==(const QString &other) const▲
Returns true if this string is 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 QString::localeAwareCompare().
[since 4.3] bool QLatin1String::operator==(const char *other) const▲
This is an overloaded function.
The other const char pointer is converted to a QString using the QString::fromUtf8() 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.
This function was introduced in Qt 4.3.
See Also▲
See also QT_NO_CAST_FROM_ASCII
[since 5.0] bool QLatin1String::operator==(const QByteArray &other) const▲
This is an overloaded function.
The other byte array is converted to a QString using the QString::fromUtf8() 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.
This function was introduced in Qt 5.0.
See Also▲
See also QT_NO_CAST_FROM_ASCII
bool QLatin1String::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 QString::localeAwareCompare().
[since 4.3] bool QLatin1String::operator>(const char *other) const▲
This is an overloaded function.
The other const char pointer is converted to a QString using the QString::fromUtf8() 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.
This function was introduced in Qt 4.3.
See Also▲
See also QT_NO_CAST_FROM_ASCII
[since 5.0] bool QLatin1String::operator>(const QByteArray &other) const▲
This is an overloaded function.
The other const char pointer is converted to a QString using the QString::fromUtf8() 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.
This function was introduced in Qt 5.0.
See Also▲
See also QT_NO_CAST_FROM_ASCII
bool QLatin1String::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 QString::localeAwareCompare().
[since 4.3] bool QLatin1String::operator>=(const char *other) const▲
This is an overloaded function.
The other const char pointer is converted to a QString using the QString::fromUtf8() 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.
This function was introduced in Qt 4.3.
See Also▲
See also QT_NO_CAST_FROM_ASCII
[since 5.0] bool QLatin1String::operator>=(const QByteArray &other) const▲
This is an overloaded function.
The other array is converted to a QString using the QString::fromUtf8() 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.
This function was introduced in Qt 5.0.
See Also▲
See also QT_NO_CAST_FROM_ASCII
[since 5.8] QLatin1Char QLatin1String::operator[](int pos) const▲
Related Non-Members▲
bool operator!=(QLatin1String s1, QLatin1String s2)▲
Returns true if string s1 is lexically unequal to string s2; otherwise returns false.
bool operator<(QLatin1String s1, QLatin1String s2)▲
Returns true if string s1 is lexically smaller than string s2; otherwise returns false.
bool operator<=(QLatin1String s1, QLatin1String s2)▲
Returns true if string s1 is lexically smaller than or equal to string s2; otherwise returns false.
bool operator==(QLatin1String s1, QLatin1String s2)▲
Returns true if string s1 is lexically equal to string s2; otherwise returns false.
bool operator>(QLatin1String s1, QLatin1String s2)▲
Returns true if string s1 is lexically greater than string s2; otherwise returns false.
bool operator>=(QLatin1String s1, QLatin1String s2)▲
Returns true if string s1 is lexically greater than or equal to string s2; otherwise returns false.