<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html> <html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <!-- qml-extending.qdoc --> <title>Extending QML - Default Property Example | Qt QML 5.12.6</title> <link rel="stylesheet" type="text/css" href="style/offline-simple.css" /> <script type="text/javascript"> document.getElementsByTagName("link").item(0).setAttribute("href", "style/offline.css"); // loading style sheet breaks anchors that were jumped to before // so force jumping to anchor again setTimeout(function() { var anchor = location.hash; // need to jump to different anchor first (e.g. none) location.hash = "#"; setTimeout(function() { location.hash = anchor; }, 0); }, 0); </script> </head> <body> <div class="header" id="qtdocheader"> <div class="main"> <div class="main-rounded"> <div class="navigationbar"> <table><tr> <td >Qt 5.12</td><td ><a href="qtqml-index.html">Qt QML</a></td><td ><a href="qmlextendingexamples.html">Qt QML Examples</a></td><td >Extending QML - Default Property Example</td></tr></table><table class="buildversion"><tr> <td id="buildversion" width="100%" align="right"><a href="qtqml-index.html">Qt 5.12.6 Reference Documentation</a></td> </tr></table> </div> </div> <div class="content"> <div class="line"> <div class="content mainContent"> <div class="sidebar"> <div class="toc"> <h3><a name="toc">Contents</a></h3> <ul> <li class="level1"><a href="#declaring-the-birthdayparty-class">Declaring the BirthdayParty Class</a></li> <li class="level1"><a href="#running-the-example">Running the Example</a></li> </ul> </div> <div class="sidebar-content" id="sidebar-content"></div></div> <h1 class="title">Extending QML - Default Property Example</h1> <span class="subtitle"></span> <!-- $$$referenceexamples/default-brief --> <p>Default Property.</p> <!-- @@@referenceexamples/default --> <!-- $$$referenceexamples/default-description --> <div class="descr"> <a name="details"></a> <p>This example builds on:</p> <ul> <li><a href="qtqml-referenceexamples-coercion-example.html">Extending QML - Inheritance and Coercion Example</a></li> <li><a href="qtqml-referenceexamples-properties-example.html">Extending QML - Object and List Property Types Example</a></li> <li><a href="qtqml-referenceexamples-adding-example.html">Extending QML - Adding Types Example</a></li> </ul> <p>The Default Property Example is a minor modification of the <a href="qtqml-referenceexamples-coercion-example.html">Extending QML - Inheritance and Coercion Example</a> that simplifies the specification of a BirthdayParty through the use of a default property.</p> <pre class="qml"> BirthdayParty { host: Boy { name: "Bob Jones" shoeSize: 12 } Boy { name: "Leo Hodges" } Boy { name: "Jack Smith" } Girl { name: "Anne Brown" } } </pre> <a name="declaring-the-birthdayparty-class"></a> <h2 id="declaring-the-birthdayparty-class">Declaring the BirthdayParty Class</h2> <p>The only difference between this example and the last, is the addition of the <code>DefaultProperty</code> class info annotation.</p> <pre class="cpp"> <span class="keyword">class</span> BirthdayParty : <span class="keyword">public</span> <span class="type">QObject</span> { Q_OBJECT Q_PROPERTY(Person <span class="operator">*</span>host READ host WRITE setHost) Q_PROPERTY(<span class="type"><a href="qqmllistproperty.html">QQmlListProperty</a></span><span class="operator"><</span>Person<span class="operator">></span> guests READ guests) Q_CLASSINFO(<span class="string">"DefaultProperty"</span><span class="operator">,</span> <span class="string">"guests"</span>) <span class="keyword">public</span>: BirthdayParty(<span class="type">QObject</span> <span class="operator">*</span>parent <span class="operator">=</span> <span class="number">0</span>); Person <span class="operator">*</span>host() <span class="keyword">const</span>; <span class="type">void</span> setHost(Person <span class="operator">*</span>); <span class="type"><a href="qqmllistproperty.html">QQmlListProperty</a></span><span class="operator"><</span>Person<span class="operator">></span> guests(); <span class="type">int</span> guestCount() <span class="keyword">const</span>; Person <span class="operator">*</span>guest(<span class="type">int</span>) <span class="keyword">const</span>; <span class="keyword">private</span>: Person <span class="operator">*</span>m_host; <span class="type">QList</span><span class="operator"><</span>Person <span class="operator">*</span><span class="operator">></span> m_guests; }; </pre> <p>The default property specifies the property to assign to whenever an explicit property is not specified, in the case of the BirthdayParty type the guest property. It is purely a syntactic simplification, the behavior is identical to specifying the property by name, but it can add a more natural feel in many situations. The default property must be either an object or list property.</p> <a name="running-the-example"></a> <h2 id="running-the-example">Running the Example</h2> <p>The main.cpp file in the example includes a simple shell application that loads and runs the QML snippet shown at the beginning of this page.</p> <p>Files:</p> <ul> <li><a href="qtqml-referenceexamples-default-birthdayparty-cpp.html">referenceexamples/default/birthdayparty.cpp</a></li> <li><a href="qtqml-referenceexamples-default-birthdayparty-h.html">referenceexamples/default/birthdayparty.h</a></li> <li><a href="qtqml-referenceexamples-default-default-pro.html">referenceexamples/default/default.pro</a></li> <li><a href="qtqml-referenceexamples-default-default-qrc.html">referenceexamples/default/default.qrc</a></li> <li><a href="qtqml-referenceexamples-default-example-qml.html">referenceexamples/default/example.qml</a></li> <li><a href="qtqml-referenceexamples-default-main-cpp.html">referenceexamples/default/main.cpp</a></li> <li><a href="qtqml-referenceexamples-default-person-cpp.html">referenceexamples/default/person.cpp</a></li> <li><a href="qtqml-referenceexamples-default-person-h.html">referenceexamples/default/person.h</a></li> </ul> </div> <!-- @@@referenceexamples/default --> </div> </div> </div> </div> </div> <div class="footer"> <p> <acronym title="Copyright">©</acronym> 2019 The Qt Company Ltd. Documentation contributions included herein are the copyrights of their respective owners.<br/> The documentation provided herein is licensed under the terms of the <a href="http://www.gnu.org/licenses/fdl.html">GNU Free Documentation License version 1.3</a> as published by the Free Software Foundation.<br/> Qt and respective logos are trademarks of The Qt Company Ltd. in Finland and/or other countries worldwide. All other trademarks are property of their respective owners. </p> </div> </body> </html>