qpair.html
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><!-- /home/reggie/tmp/qt-3.0-reggie-5401/qt-x11-commercial-3.0.5/doc/qpair.doc:40 --><html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>QPair Class</title><style type="text/css"><!--h3.fn,span.fn { margin-left: 1cm; text-indent: -1cm; }a:link { color: #004faf; text-decoration: none }a:visited { color: #672967; text-decoration: none }body { background: #ffffff; color: black; }--></style></head><body><table border="0" cellpadding="0" cellspacing="0" width="100%"><tr bgcolor="#E5E5E5"><td valign=center> <a href="index.html"><font color="#004faf">Home</font></a> | <a href="classes.html"><font color="#004faf">All Classes</font></a> | <a href="mainclasses.html"><font color="#004faf">Main Classes</font></a> | <a href="annotated.html"><font color="#004faf">Annotated</font></a> | <a href="groups.html"><font color="#004faf">Grouped Classes</font></a> | <a href="functions.html"><font color="#004faf">Functions</font></a></td><td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>QPair Class Reference</h1><p>The QPair class is a value-based template class that provides a pair of elements.<a href="#details">More...</a><p><tt>#include <<a href="qpair-h.html">qpair.h</a>></tt><p><a href="qpair-members.html">List of all member functions.</a><h2>Public Members</h2><ul><li><div class=fn>typedef T1 <a href="#first_type"><b>first_type</b></a></div></li><li><div class=fn>typedef T2 <a href="#second_type"><b>second_type</b></a></div></li><li><div class=fn><a href="#QPair"><b>QPair</b></a> ()</div></li><li><div class=fn><a href="#QPair-2"><b>QPair</b></a> ( const T1 & t1, const T2 & t2 )</div></li></ul><h2>Related Functions</h2><ul><li><div class=fn>QPair <a href="#qMakePair"><b>qMakePair</b></a> ( T1 t1, T2 t2 )</div></li></ul><hr><a name="details"></a><h2>Detailed Description</h2>The QPair class is a value-based template class that provides a pair of elements.<p> <p> QPair is a Qt implementation of an STL-like pair. Itcan be used in your application if the standard pair<> is notavailable. <p> QPair<T1, T2> defines a template instance to createa pair of values that contains two values of type T1 and T2. Pleasenote that QPair does not store pointers to the two elements; itholds a copy of every member. This is why thesekinds of classes are called <em>value based</em>. If you're interestedin <em>pointer based</em> classes see, for example, <a href="qptrlist.html">QPtrList</a> and <a href="qdict.html">QDict</a>.<p> QPair holds one copy of type T1 and one copy of type T2, but doesnot provide iterators to access these elements. Rather, the twoelements (<tt>first</tt> and <tt>second</tt>) are public member variables of thepair. QPair owns the contained elements. For more relaxed ownershipsemantics, see <a href="qptrcollection.html">QPtrCollection</a> and friends which are pointer-basedcontainers.<p> Some classes cannot be used within a QPair: for example, all classesderived from <a href="qobject.html">QObject</a> and thus all classes that implement widgets.Only "values" can be used in a QPair. To qualify as a value the classmust provide:<p> <ul><li> A copy constructor<li> An assignment operator<li> A constructor that takes no argument</ul><p> Note that C++ defaults to field-by-field assignment operators andcopy constructors if no explicit version is supplied. In many casesthis is sufficient.<p> QPair uses an STL-like syntax to manipulate and address the objectsit contains. See the <a href="qtl.html">QTL documentation</a> formore information.<p> Functions that need to return two values can use a QPair. The<a href="qtl.html#qMakePair">qMakePair()</a> convenience functionmakes it easy to create QPair objects.<p>See also <a href="qtl.html">Qt Template Library Classes</a>, <a href="shared.html">Implicitly and Explicitly Shared Classes</a> and <a href="tools.html">Non-GUI Classes</a>.<hr><h2>Member Type Documentation</h2><h3 class=fn><a name="first_type"></a>QPair::first_type</h3> The type of the first element in the pair. <h3 class=fn><a name="second_type"></a>QPair::second_type</h3> The type of the second element in the pair. <hr><h2>Member Function Documentation</h2><h3 class=fn><a name="QPair"></a>QPair::QPair ()</h3> Constructs an empty pair. The <tt>first</tt> and <tt>second</tt> elementsare default constructed. <h3 class=fn><a name="QPair-2"></a>QPair::QPair ( const T1 & t1, const T2 & t2 )</h3> Constructs a pair and initializes the <tt>first</tt> element with <em>t1</em>and the <tt>second</tt> element with <em>t2</em>.<hr><h2>Related Functions</h2><h3 class=fn><a href="qpair.html">QPair</a> <a name="qMakePair"></a>qMakePair ( T1 t1, T2 t2 )</h3><p> <p> This is a template convenience function. It is used to create aQPair<> object that contains <em>t1</em> and <em>t2</em>. For example:<pre> <a href="qmap.html">QMap</a><QString,QString> m; m.<a href="qmap.html#insert">insert</a>( <a href="#qMakePair">qMakePair</a>("Clinton", "Bill") );</pre> <p> The above code is equivalent to:<pre> <a href="qmap.html">QMap</a><QString,QString> m; QPair<QString,QString> p( "Clinton", "Bill" ); m.<a href="qmap.html#insert">insert</a>( p );</pre> <!-- eof --><hr><p>This file is part of the <a href="index.html">Qt toolkit</a>.Copyright © 1995-2002<a href="http://www.trolltech.com/">Trolltech</a>. All Rights Reserved.<p><address><hr><div align=center><table width=100% cellspacing=0 border=0><tr><td>Copyright © 2002 <a href="http://www.trolltech.com">Trolltech</a><td><a href="http://www.trolltech.com/trademarks.html">Trademarks</a><td align=right><div align=right>Qt version 3.0.5</div></table></div></address></body></html>⌨️ 快捷键说明
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