<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html> <html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <!-- factorial.qdoc --> <title>Factorial States Example | Qt Widgets 5.12.2</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="qtwidgets-index.html">Qt Widgets</a></td><td >Factorial States Example</td></tr></table><table class="buildversion"><tr> <td id="buildversion" width="100%" align="right"><a href="qtwidgets-index.html">Qt 5.12.2 Reference Documentation</a></td> </tr></table> </div> </div> <div class="content"> <div class="line"> <div class="content mainContent"> <div class="sidebar"><div class="sidebar-content" id="sidebar-content"></div></div> <h1 class="title">Factorial States Example</h1> <span class="subtitle"></span> <!-- $$$statemachine/factorial-brief --> <p>The Factorial States example shows how to use <a href="../qtcore/statemachine-api.html">The State Machine Framework</a> to calculate the factorial of an integer.</p> <!-- @@@statemachine/factorial --> <!-- $$$statemachine/factorial-description --> <div class="descr"> <a name="details"></a> <p>The statechart for calculating the factorial looks as follows:</p> <p class="centerAlign"><img src="images/factorial-example.png" alt="" /></p><p>In other words, the state machine calculates the factorial of 6 and prints the result.</p> <pre class="cpp"> <span class="keyword">class</span> Factorial : <span class="keyword">public</span> <span class="type"><a href="../qtcore/qobject.html">QObject</a></span> { Q_OBJECT Q_PROPERTY(<span class="type">int</span> x READ x WRITE setX) Q_PROPERTY(<span class="type">int</span> fac READ fac WRITE setFac) <span class="keyword">public</span>: Factorial(<span class="type"><a href="../qtcore/qobject.html">QObject</a></span> <span class="operator">*</span>parent <span class="operator">=</span> <span class="number">0</span>) : <span class="type"><a href="../qtcore/qobject.html">QObject</a></span>(parent)<span class="operator">,</span> m_x(<span class="operator">-</span><span class="number">1</span>)<span class="operator">,</span> m_fac(<span class="number">1</span>) { } <span class="type">int</span> x() <span class="keyword">const</span> { <span class="keyword">return</span> m_x; } <span class="type">void</span> setX(<span class="type">int</span> x) { <span class="keyword">if</span> (x <span class="operator">=</span><span class="operator">=</span> m_x) <span class="keyword">return</span>; m_x <span class="operator">=</span> x; <span class="keyword">emit</span> xChanged(x); } <span class="type">int</span> fac() <span class="keyword">const</span> { <span class="keyword">return</span> m_fac; } <span class="type">void</span> setFac(<span class="type">int</span> fac) { m_fac <span class="operator">=</span> fac; } Q_SIGNALS: <span class="type">void</span> xChanged(<span class="type">int</span> value); <span class="keyword">private</span>: <span class="type">int</span> m_x; <span class="type">int</span> m_fac; }; </pre> <p>The Factorial class is used to hold the data of the computation, <code>x</code> and <code>fac</code>. It also provides a signal that's emitted whenever the value of <code>x</code> changes.</p> <pre class="cpp"> <span class="keyword">class</span> FactorialLoopTransition : <span class="keyword">public</span> <span class="type"><a href="../qtcore/qsignaltransition.html">QSignalTransition</a></span> { <span class="keyword">public</span>: FactorialLoopTransition(Factorial <span class="operator">*</span>fact) : <span class="type"><a href="../qtcore/qsignaltransition.html">QSignalTransition</a></span>(fact<span class="operator">,</span> SIGNAL(xChanged(<span class="type">int</span>)))<span class="operator">,</span> m_fact(fact) {} bool eventTest(<span class="type"><a href="../qtcore/qevent.html">QEvent</a></span> <span class="operator">*</span>e) override { <span class="keyword">if</span> (<span class="operator">!</span><span class="type"><a href="../qtcore/qsignaltransition.html">QSignalTransition</a></span><span class="operator">::</span>eventTest(e)) <span class="keyword">return</span> <span class="keyword">false</span>; <span class="type"><a href="../qtcore/qstatemachine.html">QStateMachine</a></span><span class="operator">::</span>SignalEvent <span class="operator">*</span>se <span class="operator">=</span> <span class="keyword">static_cast</span><span class="operator"><</span><span class="type"><a href="../qtcore/qstatemachine.html">QStateMachine</a></span><span class="operator">::</span>SignalEvent<span class="operator">*</span><span class="operator">></span>(e); <span class="keyword">return</span> se<span class="operator">-</span><span class="operator">></span>arguments()<span class="operator">.</span>at(<span class="number">0</span>)<span class="operator">.</span>toInt() <span class="operator">></span> <span class="number">1</span>; } <span class="type">void</span> onTransition(<span class="type"><a href="../qtcore/qevent.html">QEvent</a></span> <span class="operator">*</span>e) override { <span class="type"><a href="../qtcore/qstatemachine.html">QStateMachine</a></span><span class="operator">::</span>SignalEvent <span class="operator">*</span>se <span class="operator">=</span> <span class="keyword">static_cast</span><span class="operator"><</span><span class="type"><a href="../qtcore/qstatemachine.html">QStateMachine</a></span><span class="operator">::</span>SignalEvent<span class="operator">*</span><span class="operator">></span>(e); <span class="type">int</span> x <span class="operator">=</span> se<span class="operator">-</span><span class="operator">></span>arguments()<span class="operator">.</span>at(<span class="number">0</span>)<span class="operator">.</span>toInt(); <span class="type">int</span> fac <span class="operator">=</span> m_fact<span class="operator">-</span><span class="operator">></span>property(<span class="string">"fac"</span>)<span class="operator">.</span>toInt(); m_fact<span class="operator">-</span><span class="operator">></span>setProperty(<span class="string">"fac"</span><span class="operator">,</span> x <span class="operator">*</span> fac); m_fact<span class="operator">-</span><span class="operator">></span>setProperty(<span class="string">"x"</span><span class="operator">,</span> x <span class="operator">-</span> <span class="number">1</span>); } <span class="keyword">private</span>: Factorial <span class="operator">*</span>m_fact; }; </pre> <p>The FactorialLoopTransition class implements the guard (<code>x</code> > 1) and calculations (<code>fac</code> = <code>x</code> * <code>fac</code>; <code>x</code> = <code>x</code> - 1) of the factorial loop.</p> <pre class="cpp"> <span class="keyword">class</span> FactorialDoneTransition : <span class="keyword">public</span> <span class="type"><a href="../qtcore/qsignaltransition.html">QSignalTransition</a></span> { <span class="keyword">public</span>: FactorialDoneTransition(Factorial <span class="operator">*</span>fact) : <span class="type"><a href="../qtcore/qsignaltransition.html">QSignalTransition</a></span>(fact<span class="operator">,</span> SIGNAL(xChanged(<span class="type">int</span>)))<span class="operator">,</span> m_fact(fact) {} bool eventTest(<span class="type"><a href="../qtcore/qevent.html">QEvent</a></span> <span class="operator">*</span>e) override { <span class="keyword">if</span> (<span class="operator">!</span><span class="type"><a href="../qtcore/qsignaltransition.html">QSignalTransition</a></span><span class="operator">::</span>eventTest(e)) <span class="keyword">return</span> <span class="keyword">false</span>; <span class="type"><a href="../qtcore/qstatemachine.html">QStateMachine</a></span><span class="operator">::</span>SignalEvent <span class="operator">*</span>se <span class="operator">=</span> <span class="keyword">static_cast</span><span class="operator"><</span><span class="type"><a href="../qtcore/qstatemachine.html">QStateMachine</a></span><span class="operator">::</span>SignalEvent<span class="operator">*</span><span class="operator">></span>(e); <span class="keyword">return</span> se<span class="operator">-</span><span class="operator">></span>arguments()<span class="operator">.</span>at(<span class="number">0</span>)<span class="operator">.</span>toInt() <span class="operator"><</span><span class="operator">=</span> <span class="number">1</span>; } <span class="type">void</span> onTransition(<span class="type"><a href="../qtcore/qevent.html">QEvent</a></span> <span class="operator">*</span>) override { fprintf(stdout<span class="operator">,</span> <span class="string">"%d\n"</span><span class="operator">,</span> m_fact<span class="operator">-</span><span class="operator">></span>property(<span class="string">"fac"</span>)<span class="operator">.</span>toInt()); } <span class="keyword">private</span>: Factorial <span class="operator">*</span>m_fact; }; </pre> <p>The FactorialDoneTransition class implements the guard (<code>x</code> <= 1) that terminates the factorial computation. It also prints the final result to standard output.</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><span class="operator">*</span>argv) { <span class="type"><a href="../qtcore/qcoreapplication.html">QCoreApplication</a></span> app(argc<span class="operator">,</span> argv); Factorial factorial; <span class="type"><a href="../qtcore/qstatemachine.html">QStateMachine</a></span> machine; </pre> <p>The application's main() function first creates the application object, a Factorial object and a state machine.</p> <pre class="cpp"> <span class="type"><a href="../qtcore/qstate.html">QState</a></span> <span class="operator">*</span>compute <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="../qtcore/qstate.html">QState</a></span>(<span class="operator">&</span>machine); compute<span class="operator">-</span><span class="operator">></span>assignProperty(<span class="operator">&</span>factorial<span class="operator">,</span> <span class="string">"fac"</span><span class="operator">,</span> <span class="number">1</span>); compute<span class="operator">-</span><span class="operator">></span>assignProperty(<span class="operator">&</span>factorial<span class="operator">,</span> <span class="string">"x"</span><span class="operator">,</span> <span class="number">6</span>); compute<span class="operator">-</span><span class="operator">></span>addTransition(<span class="keyword">new</span> FactorialLoopTransition(<span class="operator">&</span>factorial)); </pre> <p>The <code>compute</code> state is created, and the initial values of <code>x</code> and <code>fac</code> are defined. A FactorialLoopTransition object is created and added to the state.</p> <pre class="cpp"> <span class="type"><a href="../qtcore/qfinalstate.html">QFinalState</a></span> <span class="operator">*</span>done <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="../qtcore/qfinalstate.html">QFinalState</a></span>(<span class="operator">&</span>machine); FactorialDoneTransition <span class="operator">*</span>doneTransition <span class="operator">=</span> <span class="keyword">new</span> FactorialDoneTransition(<span class="operator">&</span>factorial); doneTransition<span class="operator">-</span><span class="operator">></span>setTargetState(done); compute<span class="operator">-</span><span class="operator">></span>addTransition(doneTransition); </pre> <p>A final state, <code>done</code>, is created, and a FactorialDoneTransition object is created with <code>done</code> as its target state. The transition is then added to the <code>compute</code> state.</p> <pre class="cpp"> machine<span class="operator">.</span>setInitialState(compute); <span class="type"><a href="../qtcore/qobject.html">QObject</a></span><span class="operator">::</span>connect(<span class="operator">&</span>machine<span class="operator">,</span> <span class="operator">&</span><span class="type"><a href="../qtcore/qstatemachine.html">QStateMachine</a></span><span class="operator">::</span>finished<span class="operator">,</span> <span class="operator">&</span>app<span class="operator">,</span> <span class="type"><a href="../qtcore/qcoreapplication.html">QCoreApplication</a></span><span class="operator">::</span>quit); machine<span class="operator">.</span>start(); <span class="keyword">return</span> app<span class="operator">.</span>exec(); } </pre> <p>The machine's initial state is set to be the <code>compute</code> state. We connect the <a href="../qtcore/qstate.html#finished">QStateMachine::finished</a>() signal to the <a href="../qtcore/qcoreapplication.html#quit">QCoreApplication::quit</a>() slot, so the application will quit when the state machine's work is done. Finally, the state machine is started, and the application's event loop is entered.</p> <p>Files:</p> <ul> <li><a href="qtwidgets-statemachine-factorial-factorial-pro.html">statemachine/factorial/factorial.pro</a></li> <li><a href="qtwidgets-statemachine-factorial-main-cpp.html">statemachine/factorial/main.cpp</a></li> </ul> </div> <!-- @@@statemachine/factorial --> </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>