Qt 4.0: QStringList Class Reference

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# QStringList Class Reference
[QtCore module]

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

    #include <QStringList>

Inherits QList<QString>.

Note: All the functions in this class are reentrant.

- List of all members, including inherited members
- Qt 3 support members

### Public Functions

- QStringList ()
- QStringList ( const QString & str )
- QStringList ( const QStringList & other )
- QStringList ( const QList<QString> & other )
- bool contains ( const QString & str, Qt::CaseSensitivity cs = Qt::CaseSensitive ) const
- QStringList filter ( const QString & str, Qt::CaseSensitivity cs = Qt::CaseSensitive ) const
- QStringList filter ( const QRegExp & rx ) const
- int indexOf ( const QRegExp & rx, int from = 0 ) const
- QString join ( const QString & sep ) const
- int lastIndexOf ( const QRegExp & rx, int from = -1 ) const
- QStringList & replaceInStrings ( const QString & before, const QString & after, Qt::CaseSensitivity cs = Qt::CaseSensitive )
- QStringList & replaceInStrings ( const QRegExp & rx, const QString & after )
- void sort ()
- QStringList operator+ ( const QStringList & other ) const
- QStringList & operator<< ( const QString & str )
- QStringList & operator<< ( const QStringList & other )

- 60 public functions inherited from QList

### Related Non-Members

- typedef QMutableStringListIterator
- typedef QStringListIterator
- QDataStream & operator<< ( QDataStream & out, const QStringList & list )
- QDataStream & operator>> ( QDataStream & in, QStringList & list )

### Additional Inherited Members

- 3 static public members inherited from QList

## Detailed Description

The QStringList class provides a list of strings.

QStringList inherits from QList<QString>. All of QList's functionality also applies to QStringList. For example, you can use isEmpty() to test whether the list is empty, and you can call functions like append(), prepend(), insert(), replace(), and remove() to modify a QStringList. In addition, QStringList provides a few convenience functions that make handling lists of strings easier.

Like QList, QStringList is implicitly shared. QStringList provides fast index-based access as well as fast insertions and removals. Passing string lists as value parameters is both fast and safe.

Strings can be added to a list using append(), operator+=(), or operator<<(). For example:

        QStringList fonts;
        fonts << "Arial" << "Helvetica" << "Times" << "Courier";

To iterate over a string, you can either use index positions or QList's Java-style and STL-style iterator types. Here are examples of each approach.

Indexing:

        for (int i = 0; i < fonts.size(); ++i)
            cout << fonts.at(i).ascii() << endl;

Java-style iterator:

        QStringListIterator i(fonts);
        while (i.hasNext())
            cout << i.next().ascii() << endl;

STL-style iterator:

        QStringList::const_iterator i;
        for (i = fonts.constBegin(); i != fonts.constEnd(); ++i)
            cout << (*i).ascii() << endl;

QStringListIterator and QMutableStringListIterator are simply typedefs for QListIterator<QString> and QMutableListIterator<QString>.

You can concatenate all the strings in a string list into a single string (with an optional separator) using join(). For example:

        QString str = fonts.join(",");
        // str == "Arial,Helvetica,Times,Courier"

To break up a string into a string list, use QString::split():

        QString str = "Arial,Helvetica,Times,Courier";
        QStringList list = str.split(",");
        // list: ["Arial", "Helvetica", "Times", "Courier"]

The argument to split can be a single character, a string, or a QRegExp.

You can sort a string 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 find() functions. For example:

        QStringList monospacedFonts = fonts.find(QRegExp("Courier|Fixed"));

Similarly, the replace() function calls QString::replace() on each string in the string list in turn. Here's an example that uses it to replace all occurrences of "$QTDIR" with "/usr/lib/qt" in a string list:

        QStringList files;
        files << "$QTDIR/src/moc/moc.y"
              << "$QTDIR/src/moc/moc.l"
              << "$QTDIR/include/qconfig.h";

        files.replace("$QTDIR", "/usr/lib/qt");

See also QString, QStringListIterator, and QMutableStringListIterator.

## Member Function Documentation

### QStringList::QStringList ()

Constructs an empty string list.

### QStringList::QStringList ( const QString & str )

Constructs a string list that contains one string, str. Longer lists are easily created like this:

        list = (QStringList() << str1 << str2 << str3);

### QStringList::QStringList ( const QStringList & other )

Constructs a copy of other.

This operation takes constant time, because QStringList is implicitly shared. This makes returning a QStringList from a function very fast. If a shared instance is modified, it will be copied (copy-on-write), and that takes linear time.

See also operator=().

### QStringList::QStringList ( const QList<QString> & other )

Constructs a copy of other.

This operation takes constant time, because QStringList is implicitly shared. This makes returning a QStringList from a function very fast. If a shared instance is modified, it will be copied (copy-on-write), and that takes linear time.

See also operator=().

### bool QStringList::contains ( const QString & str, Qt::CaseSensitivity cs = Qt::CaseSensitive ) const

Returns true if the list contains the string str. Does a case insensitive search if cs is Qt::CaseSensitive, otherwise the search will be case insensitive.

### QStringList QStringList::filter ( const QString & str, Qt::CaseSensitivity cs = Qt::CaseSensitive ) const

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

If cs is Qt::CaseSensitive (the default), the string comparison is case sensitive; otherwise the comparison is case insensitive.

        QStringList list;
        list << "Bill Murray" << "John Doe" << "Bill Clinton";
        list = list.filter("Bill");
        // list: ["Bill Murray", "Bill Clinton"]

See also QString::contains().

### QStringList QStringList::filter ( 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.

### int QStringList::indexOf ( const QRegExp & rx, int from = 0 ) const

Returns the index position of the first exact match of rx in the list, searching forward from index position from. Returns -1 if no item matched.

See also lastIndexOf() and QRegExp::exactMatch().

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

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

See also QString::split().

### int QStringList::lastIndexOf ( const QRegExp & rx, int from = -1 ) const

Returns the index position of the last exact match of rx in the list, searching backward from index position from. If from is -1 (the default), the search starts at the last item. Returns -1 if no item matched.

See also indexOf() and QRegExp::exactMatch().

### QStringList & QStringList::replaceInStrings ( const QString & before, const QString & after, Qt::CaseSensitivity cs = Qt::CaseSensitive )

Returns a string list where every string has had the before text replaced with the after text wherever the before text is found. The before text is matched case-sensitively or not depending on the cs flag.

Example:

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

See also QString::replace().

### QStringList & QStringList::replaceInStrings ( 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 each of the string lists's strings, with after. Returns a reference to the string list.

Example:

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

For regular expressions that contain capturing parentheses, occurrences of \1, \2, ..., in after are replaced with rx.cap(1), rx.cap(2), ...

Example:

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

See also replace().

### void QStringList::sort ()

Sorts the list of strings in ascending order (case sensitively).

Sorting is performed using Qt's qSort() algorithm, which operates in linear-logarithmic time, i.e. 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. with the keys being lower-case versions of the strings, and the values being the strings), or a QMap<int, QString> to sort the strings by some integer index.

See also qSort().

### QStringList QStringList::operator+ ( const QStringList & other ) const

Returns a string list that is the concatenation of this string list with the other string list.

See also append().

### QStringList & QStringList::operator<< ( const QString & str )

Appends string str to the string list and returns a reference to the string list.

See also append().

### QStringList & QStringList::operator<< ( const QStringList & other )

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

Appends other to the string list and returns a reference to the string list.

## Related Non-Members

### typedef QMutableStringListIterator

The QStringListIterator typedef provides a Java-style non-const iterator for QStringList.

QStringList provides both Java-style iterators and STL-style iterators. The Java-style non-const iterator is simply a typedef for QMutableListIterator<QString>.

See also QStringListIterator and QStringList::iterator.

### typedef QStringListIterator

The QStringListIterator typedef provides a Java-style const iterator for QStringList.

QStringList provides both Java-style iterators and STL-style iterators. The Java-style const iterator is simply a typedef for QListIterator<QString>.

See also QMutableStringListIterator and QStringList::const_iterator.

### QDataStream & operator<< ( QDataStream & out, const QStringList & list )

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

Writes the string list list to stream out.

See also Format of the QDataStream operators.

### QDataStream & operator>> ( QDataStream & in, QStringList & list )

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

Reads a string list from stream in into list.

See also Format of the QDataStream operators.