QPair

Section: Misc. Reference Manual Pages (3qt)
Updated: 2 February 2007
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NAME

QPair - Value-based template class that provides a pair of elements

SYNOPSIS

#include <qpair.h>

Public Members

typedef T1 first_type

typedef T2 second_type

QPair ()

QPair ( const T1 & t1, const T2 & t2 )

QPair<T1, T2> & operator= ( const QPair<T1, T2> & other )

DESCRIPTION

The QPair class is a value-based template class that provides a pair of elements.

QPair is a Qt implementation of an STL-like pair. It can be used in your application if the standard pair<> is not available on your target platforms.

QPair<T1, T2> defines a template instance to create a pair of values that contains two values of type T1 and T2. Please note that QPair does not store pointers to the two elements; it holds a copy of every member. This is why these kinds of classes are called value based. If you're interested in pointer based classes see, for example, QPtrList and QDict.

QPair holds one copy of type T1 and one copy of type T2, but does not provide iterators to access these elements. Instead, the two elements (first and second) are public member variables of the pair. QPair owns the contained elements. For more relaxed ownership semantics, see QPtrCollection and friends which are pointer-based containers.

Some classes cannot be used within a QPair: for example, all classes derived from QObject and thus all classes that implement widgets. Only "values" can be used in a QPair. To qualify as a value the class must provide:

A copy constructor
An assignment operator
A constructor that takes no arguments

Note that C++ defaults to field-by-field assignment operators and copy constructors if no explicit version is supplied. In many cases this is sufficient.

QPair uses an STL-like syntax to manipulate and address the objects it contains. See the QTL documentation for more information.

Functions that need to return two values can use a QPair.

See also Qt Template Library Classes, Implicitly and Explicitly Shared Classes, and Non-GUI Classes.

Member Type Documentation

QPair::first_type

The type of the first element in the pair.

QPair::second_type

The type of the second element in the pair.

MEMBER FUNCTION DOCUMENTATION

QPair::QPair ()

Constructs an empty pair. The first and second elements are default constructed.

QPair::QPair ( const T1 & t1, const T2 & t2 )

Constructs a pair and initializes the first element with t1 and the second element with t2.

QPair qMakePair ( T1 t1, T2 t2 )

This is a template convenience function. It is used to create a QPair<> object that contains t1 and t2.

COPYRIGHT

AUTHOR

Generated automatically from the source code.

BUGS

If you find a bug in Qt, please report it as described in http://doc.trolltech.com/bughowto.html. Good bug reports help us to help you. Thank you. The definitive Qt documentation is provided in HTML format; it is located at $QTDIR/doc/html and can be read using Qt Assistant or with a web browser. This man page is provided as a convenience for those users who prefer man pages, although this format is not officially supported by Trolltech. If you find errors in this manual page, please report them to qt-bugs@trolltech.com. Please include the name of the manual page (qpair.3qt) and the Qt version (3.3.8).