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Breadcrumbs go here --> <li><a href="all-examples.html">Examples</a></li> <li>Multiple Inheritance Example</li> </ul> </div> <div class="toolbuttons toolblock"> <ul> <li id="smallA" class="t_button">A</li> <li id="medA" class="t_button active">A</li> <li id="bigA" class="t_button">A</li> <li id="print" class="t_button"><a href="javascript:this.print();"> <span>Print</span></a></li> </ul> </div> </div> <div class="content mainContent"> <div class="toc"> <h3><a name="toc">Contents</a></h3> <ul> <li class="level1"><a href="#calculatorform-definition">CalculatorForm Definition</a></li> <li class="level1"><a href="#calculatorform-implementation">CalculatorForm Implementation</a></li> <li class="level1"><a href="#function"><tt>main()</tt> Function</a></li> </ul> </div> <h1 class="title">Multiple Inheritance Example</h1> <span class="subtitle"></span> <!-- $$$uitools/multipleinheritance-description --> <div class="descr"> <a name="details"></a> <p>Files:</p> <ul> <li><a href="uitools-multipleinheritance-calculatorform-cpp.html">uitools/multipleinheritance/calculatorform.cpp</a></li> <li><a href="uitools-multipleinheritance-calculatorform-h.html">uitools/multipleinheritance/calculatorform.h</a></li> <li><a href="uitools-multipleinheritance-calculatorform-ui.html">uitools/multipleinheritance/calculatorform.ui</a></li> <li><a href="uitools-multipleinheritance-main-cpp.html">uitools/multipleinheritance/main.cpp</a></li> <li><a href="uitools-multipleinheritance-multipleinheritance-pro.html">uitools/multipleinheritance/multipleinheritance.pro</a></li> </ul> <p>The Multiple Inheritance Example shows how to use a form created with <i>Qt Designer</i> in an application by subclassing both <a href="qwidget.html">QWidget</a> and the user interface class, which is <tt>Ui::CalculatorForm</tt>.<p class="centerAlign"><img src="images/multipleinheritance-example.png" alt="" /></p><p>To subclass the <tt>calculatorform.ui</tt> file and ensure that <tt>qmake</tt> processes it with the <tt>uic</tt>, we have to include <tt>calculatorform.ui</tt> in the <tt>.pro</tt> file, as shown below:</p> <pre class="cpp"> SOURCES = calculatorform.cpp main.cpp HEADERS = calculatorform.h FORMS = calculatorform.ui</pre> <p>When the project is compiled, the <tt>uic</tt> will generate a corresponding <tt>ui_calculatorform.h</tt>.</p> <a name="calculatorform-definition"></a> <h2>CalculatorForm Definition</h2> <p>In the <tt>CalculatorForm</tt> definition, we include the <tt>ui_calculatorform.h</tt> that was generated earlier.</p> <pre class="cpp"> <span class="preprocessor">#include "ui_calculatorform.h"</span></pre> <p>As mentioned earlier, the class is a subclass of both <a href="qwidget.html">QWidget</a> and <tt>Ui::CalculatorForm</tt>.</p> <pre class="cpp"> <span class="keyword">class</span> CalculatorForm : <span class="keyword">public</span> <span class="type"><a href="qwidget.html">QWidget</a></span><span class="operator">,</span> <span class="keyword">private</span> Ui<span class="operator">::</span>CalculatorForm { Q_OBJECT <span class="keyword">public</span>: CalculatorForm(<span class="type"><a href="qwidget.html">QWidget</a></span> <span class="operator">*</span>parent <span class="operator">=</span> <span class="number">0</span>); <span class="keyword">private</span> <span class="keyword">slots</span>: <span class="type">void</span> on_inputSpinBox1_valueChanged(<span class="type">int</span> value); <span class="type">void</span> on_inputSpinBox2_valueChanged(<span class="type">int</span> value); };</pre> <p>Two slots are defined according to the <a href="designer-using-a-ui-file.html#automatic-connections">automatic connection</a> naming convention required by <tt>uic</tt>. This is to ensure that <a href="qmetaobject.html">QMetaObject</a>'s auto-connection facilities connect all the signals and slots involved automatically.</p> <a name="calculatorform-implementation"></a> <h2>CalculatorForm Implementation</h2> <p>In the constructor, we call <tt>setupUi()</tt> to load the user interface file. Note that we do not need the <tt>ui</tt> prefix as <tt>CalculatorForm</tt> is a subclass of the user interface class.</p> <pre class="cpp"> CalculatorForm<span class="operator">::</span>CalculatorForm(<span class="type"><a href="qwidget.html">QWidget</a></span> <span class="operator">*</span>parent) : <span class="type"><a href="qwidget.html">QWidget</a></span>(parent) { setupUi(<span class="keyword">this</span>); }</pre> <p>We include two slots, <tt>on_inputSpinBox1_valueChanged()</tt> and <tt>on_inputSpinBox2_valueChanged()</tt>. These slots respond to the <a href="qspinbox.html#valueChanged">valueChanged()</a> signal that both spin boxes emit. Whenever there is a change in one spin box's value, we take that value and add it to whatever value the other spin box has.</p> <pre class="cpp"> <span class="type">void</span> CalculatorForm<span class="operator">::</span>on_inputSpinBox1_valueChanged(<span class="type">int</span> value) { outputWidget<span class="operator">-</span><span class="operator">></span>setText(<span class="type"><a href="qstring.html">QString</a></span><span class="operator">::</span>number(value <span class="operator">+</span> inputSpinBox2<span class="operator">-</span><span class="operator">></span>value())); } <span class="type">void</span> CalculatorForm<span class="operator">::</span>on_inputSpinBox2_valueChanged(<span class="type">int</span> value) { outputWidget<span class="operator">-</span><span class="operator">></span>setText(<span class="type"><a href="qstring.html">QString</a></span><span class="operator">::</span>number(value <span class="operator">+</span> inputSpinBox1<span class="operator">-</span><span class="operator">></span>value())); }</pre> <a name="function"></a> <h2><tt>main()</tt> Function</h2> <p>The <tt>main()</tt> function instantiates <a href="qapplication.html">QApplication</a> and <tt>CalculatorForm</tt>. The <tt>calculator</tt> object is displayed by invoking the <a href="qwidget.html#show">show()</a> function.</p> <pre class="cpp"> <span class="type">int</span> main(<span class="type">int</span> argc<span class="operator">,</span> <span class="type">char</span> <span class="operator">*</span>argv<span class="operator">[</span><span class="operator">]</span>) { <span class="type"><a href="qapplication.html">QApplication</a></span> app(argc<span class="operator">,</span> argv); CalculatorForm calculator; <span class="preprocessor">#if defined(Q_OS_SYMBIAN)</span> calculator<span class="operator">.</span>showMaximized(); <span class="preprocessor">#else</span> calculator<span class="operator">.</span>show(); <span class="preprocessor">#endif</span> <span class="keyword">return</span> app<span class="operator">.</span>exec(); }</pre> <p>There are various approaches to include forms into applications. The Multiple Inheritance approach is just one of them. See <a href="designer-using-a-ui-file.html">Using a Designer UI File in Your Application</a> for more information on the other approaches available.</p> </div> <!-- @@@uitools/multipleinheritance --> </div> </div> </div> <div class="ft"> <span></span> </div> </div> <div class="footer"> <p> <acronym title="Copyright">©</acronym> 2013 Digia Plc and/or its subsidiaries. Documentation contributions included herein are the copyrights of their respective owners.</p> <br /> <p> 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.</p> <p> Documentation sources may be obtained from <a href="http://www.qt-project.org"> www.qt-project.org</a>.</p> <br /> <p> Digia, Qt and their respective logos are trademarks of Digia Plc in Finland and/or other countries worldwide. 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