QStringList Class

Home | All Classes | Main Classes | Annotated | Grouped Classes | Functions |

# QStringList Class Reference

The QStringList class provides a list of strings. More...

All the functions in this class are reentrant when Qt is built with thread support.

`#include <qstringlist.h>`

Inherits QValueList<QString>.

List of all member functions.

## Public Members

- QStringList ()
- QStringList ( const QStringList & l )
- QStringList ( const QValueList<QString> & l )
- QStringList ( const QString & i )
- QStringList ( const char * i )
- void sort ()
- QString join ( const QString & sep ) const
- QStringList grep ( const QString & str, bool cs = TRUE ) const
- QStringList grep ( const QRegExp & rx ) const
- QStringList & gres ( const QString & before, const QString & after, bool cs = TRUE )
- QStringList & gres ( const QRegExp & rx, const QString & after )

## Static Public Members

- QStringList fromStrList ( const QStrList & ascii )
- QStringList split ( const QString & sep, const QString & str, bool allowEmptyEntries = FALSE )
- QStringList split ( const QChar & sep, const QString & str, bool allowEmptyEntries = FALSE )
- QStringList split ( const QRegExp & sep, const QString & str, bool allowEmptyEntries = FALSE )

## Detailed Description

The QStringList class provides a list of strings.

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, so 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 string lists by value; 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]`

Converts from an ASCII-QStrList ascii to a QStringList (Unicode).

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

Returns a list of all the strings containing the substring str.

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

        QStringList list;
        list << "Bill Gates" << "John Doe" << "Bill Clinton";
        list = list.grep( "Bill" );
        // list == ["Bill Gates", "Bill Clinton"]

See also QString::find().

### QStringList QStringList::grep ( const QRegExp & rx ) const

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

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

See also QString::find().

### QStringList & QStringList::gres ( const QString & before, const QString & after, bool cs = TRUE )

Replaces every occurrence of the string before in the strings that constitute the string list with the string after. Returns a reference to the string list.

If cs is TRUE, the search is case sensitive; otherwise the search is case insensitive.

Example:

        QStringList list;
        list << "alpha" << "beta" << "gamma" << "epsilon";
        list.gres( "a", "o" );
        // list == ["olpho", "beto", "gommo", "epsilon"]

See also QString::replace().

### QStringList & QStringList::gres ( const QRegExp & rx, const QString & after )

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

Replaces every occurrence of the regexp rx in the string with after. Returns a reference to the string list.

Example:

        QStringList list;
        list << "alpha" << "beta" << "gamma" << "epsilon";
        list.gres( QRegExp("^a"), "o" );
        // list == ["olpha", "beta", "gamma", "epsilon"]

For regexps containing capturing parentheses, occurrences of \1, \2, ..., in after are replaced with rx.cap(1), cap(2), ...

Example:

        QStringList list;
        list << "Bill Clinton" << "Gates, Bill";
        list.gres( QRegExp("^(.*), (.*)$"), "\\2 \\1" );
        // list == ["Bill Clinton", "Bill Gates"]

See also QString::replace().

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

Joins the string list into a single string with each element separated by the string sep (which can be empty).

See also split().

Examples: fileiconview/qfileiconview.cpp and toplevel/options.ui.h.

### void QStringList::sort ()

Sorts the list of strings in ascending case-sensitive order.

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]`

Splits the string str into strings wherever the regular expression sep occurs, and returns the list of those strings.

If allowEmptyEntries is TRUE, a null 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 single element list with the element containing 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 is an overloaded member function, provided for convenience. It behaves essentially like the above function.

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, a null 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 is an overloaded member function, provided for convenience. It behaves essentially like the above function.

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

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

This file is part of the Qt toolkit. Copyright © 1995-2007 Trolltech. All Rights Reserved.