QStringList Class Reference

Detailed Description

It is used to store and manipulate strings that logically belong together. Essentially QStringList is a QValueList of QString objects. Unlike QStrList, which stores pointers to characters, QStringList holds real QString objects. It is the class of choice whenever you work with Unicode strings. QStringList is part of the Qt Template Library.

Like QString itself, QStringList objects are implicitly shared. Passing them around as value-parameters is both fast and safe.

Strings can be added to a list using append(), operator+=() or operator<<(), e.g.

    QStringList fonts;
    fonts.append( "Times" );
    fonts += "Courier";
    fonts += "Courier New";
    fonts << "Helvetica [Cronyx]" << "Helvetica [Adobe]";
    

String lists have an iterator, QStringList::Iterator(), e.g.

    for ( QStringList::Iterator it = fonts.begin(); it != fonts.end(); ++it ) {
        cout << *it << ":";
    }
    cout << endl;
    // Output:
    //  Times:Courier:Courier New:Helvetica [Cronyx]:Helvetica [Adobe]:
    

Many Qt functions return const string lists; to iterate over these you should make a copy and iterate over the copy.

You can concatenate all the strings in a string list into a single string (with an optional separator) using join(), e.g.

    QString allFonts = fonts.join( ", " );
    cout << allFonts << endl;
    // Output:
    //  Times, Courier, Courier New, Helvetica [Cronyx], Helvetica [Adobe]
    

You can sort the list with sort(), and extract a new list which contains only those strings which contain a particular substring (or match a particular regular expression) using the grep() functions, e.g.

    fonts.sort();
    cout << fonts.join( ", " ) << endl;
    // Output:
    //  Courier, Courier New, Helvetica [Adobe], Helvetica [Cronyx], Times

    QStringList helveticas = fonts.grep( "Helvetica" );
    cout << helveticas.join( ", " ) << endl;
    // Output:
    //  Helvetica [Adobe], Helvetica [Cronyx]
    

Existing strings can be split into string lists with character, string or regular expression separators, e.g.

    QString s = "Red\tGreen\tBlue";
    QStringList colors = QStringList::split( "\t", s );
    cout << colors.join( ", " ) << endl;
    // Output:
    //  Red, Green, Blue
    

See also Implicitly and Explicitly Shared Classes, Text Related Classes and Non-GUI Classes.

Member Function Documentation

QStringList::QStringList ()

Creates an empty string list.

QStringList::QStringList ( const QStringList & l )

Creates a copy of the list l. This function is very fast because QStringList is implicitly shared. In most situations this acts like a deep copy, for example, if this list or the original one or some other list referencing the same shared data is modified, the modifying list first makes a copy, i.e. copy-on-write. In a threaded environment you may require a real deep copy .

QStringList::QStringList ( const QValueList<QString> & l )

Constructs a new string list that is a copy of l.

QStringList::QStringList ( const QString & i )

Constructs a string list consisting of the single string i. Longer lists are easily created as follows:

    QStringList items;
    items << "Buy" << "Sell" << "Update" << "Value";
    

QStringList::QStringList ( const char * i )

Constructs a string list consisting of the single latin-1 string i.

QStringList QStringList::fromStrList ( const QStrList & ascii ) [static]

QStringList QStringList::grep ( const QString & str, bool cs = TRUE ) const

If cs is TRUE, the grep is done case-sensitively; otherwise case is ignored.

QStringList QStringList::grep ( const QRegExp & expr ) const

Returns a list of all the strings that match the regular expression expr.

QString QStringList::join ( const QString & sep ) const

See also split().

void QStringList::sort ()

Sorting is very fast. It uses the Qt Template Library's efficient HeapSort implementation that has a time complexity of O(n*log n).

If you want to sort your strings in an arbitrary order consider using a QMap. For example you could use a QMap<QString,QString> to create a case-insensitive ordering (e.g. mapping the lowercase text to the text), or a QMap<int,QString> to sort the strings by some integer index, etc.

Example: themes/themes.cpp.

QStringList QStringList::split ( const QRegExp & sep, const QString & str, bool allowEmptyEntries = FALSE ) [static]

If allowEmptyEntries is TRUE, an empty string is inserted in the list wherever the separator matches twice without intervening text.

For example, if you split the string "a,,b,c" on commas, split() returns the three-item list "a", "b", "c" if allowEmptyEntries is FALSE (the default), and the four-item list "a", "", "b", "c" if allowEmptyEntries is TRUE.

If sep does not match anywhere in str, split() returns a list consisting of the single string str.

See also join() and QString::section().

Examples: chart/element.cpp, dirview/dirview.cpp and network/httpd/httpd.cpp.

QStringList QStringList::split ( const QString & sep, const QString & str, bool allowEmptyEntries = FALSE ) [static]

This version of the function uses a QString as separator, rather than a regular expression.

If sep is an empty string, the return value is a list of one-character strings: split( QString( "" ), "four" ) returns the four-item list, "f", "o", "u", "r".

If allowEmptyEntries is TRUE, an empty string is inserted in the list wherever the separator matches twice without intervening text.

See also join() and QString::section().

QStringList QStringList::split ( const QChar & sep, const QString & str, bool allowEmptyEntries = FALSE ) [static]

This version of the function uses a QChar as separator, rather than a regular expression.

See also join() and QString::section().

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