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Breadcrumbs go here --> <li><a href="all-examples.html">Examples</a></li> <li>QtScript Calculator 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"> <h1 class="title">QtScript Calculator Example</h1> <span class="subtitle"></span> <!-- $$$script/calculator-description --> <div class="descr"> <a name="details"></a> <p>Files:</p> <ul> <li><a href="script-calculator-calculator-js.html">script/calculator/calculator.js</a></li> <li><a href="script-calculator-calculator-ui.html">script/calculator/calculator.ui</a></li> <li><a href="script-calculator-main-cpp.html">script/calculator/main.cpp</a></li> <li><a href="script-calculator-calculator-pro.html">script/calculator/calculator.pro</a></li> <li><a href="script-calculator-calculator-qrc.html">script/calculator/calculator.qrc</a></li> </ul> <p>In the <a href="qtscript.html">QtScript</a> Calculator example, we show how to implement the functionality of a calculator widget.<p class="centerAlign"><img src="images/qtscript-calculator-example.png" alt="" /></p><p>The program logic in this example is a fairly straight port of the logic in the C++ <a href="widgets-calculator.html">Calculator Example</a>. The graphical user interface is defined in a UI file.</p> <p>The C++ part of the example consists of four steps:</p> <ul> <li>Evaluate the script code that defines the <tt>Calculator</tt> class.<pre class="cpp"> <span class="type"><a href="qscriptengine.html">QScriptEngine</a></span> engine; <span class="type"><a href="qstring.html">QString</a></span> scriptFileName(<span class="string">":/calculator.js"</span>); <span class="type"><a href="qfile.html">QFile</a></span> scriptFile(scriptFileName); scriptFile<span class="operator">.</span>open(<span class="type"><a href="qiodevice.html">QIODevice</a></span><span class="operator">::</span>ReadOnly); engine<span class="operator">.</span>evaluate(scriptFile<span class="operator">.</span>readAll()<span class="operator">,</span> scriptFileName); scriptFile<span class="operator">.</span>close();</pre> </li> <li>Create a widget from the UI file using <a href="quiloader.html">QUiLoader</a>.<pre class="cpp"> <span class="type"><a href="quiloader.html">QUiLoader</a></span> loader; <span class="type"><a href="qfile.html">QFile</a></span> uiFile(<span class="string">":/calculator.ui"</span>); uiFile<span class="operator">.</span>open(<span class="type"><a href="qiodevice.html">QIODevice</a></span><span class="operator">::</span>ReadOnly); <span class="type"><a href="qwidget.html">QWidget</a></span> <span class="operator">*</span>ui <span class="operator">=</span> loader<span class="operator">.</span>load(<span class="operator">&</span>uiFile); uiFile<span class="operator">.</span>close();</pre> </li> <li>Call the Calculator constructor function to create a new <tt>Calculator</tt> script object, passing the widget as argument.<pre class="cpp"> <span class="type"><a href="qscriptvalue.html">QScriptValue</a></span> ctor <span class="operator">=</span> engine<span class="operator">.</span>evaluate(<span class="string">"Calculator"</span>); <span class="type"><a href="qscriptvalue.html">QScriptValue</a></span> scriptUi <span class="operator">=</span> engine<span class="operator">.</span>newQObject(ui<span class="operator">,</span> <span class="type"><a href="qscriptengine.html">QScriptEngine</a></span><span class="operator">::</span>ScriptOwnership); <span class="type"><a href="qscriptvalue.html">QScriptValue</a></span> calc <span class="operator">=</span> ctor<span class="operator">.</span>construct(<span class="type">QScriptValueList</span>() <span class="operator"><</span><span class="operator"><</span> scriptUi);</pre> </li> <li>Show the widget and start the application event loop.<pre class="cpp"> ui<span class="operator">-</span><span class="operator">></span>show(); <span class="keyword">return</span> app<span class="operator">.</span>exec();</pre> </li> </ul> <p>On the script side, the <tt>Calculator</tt> constructor function initializes the instance variables of the new <tt>Calculator</tt> object, and connects the clicked() signal of the form's buttons to corresponding functions defined in the <tt>Calculator</tt> prototype object; the effect is that when a button is clicked, the proper script function will be invoked to carry out the operation.</p> <pre class="js"> <span class="keyword">function</span> <span class="name">Calculator</span>(<span class="name">ui</span>) { this.<span class="name">ui</span> <span class="operator">=</span> <span class="name">ui</span>; this.<span class="name">pendingAdditiveOperator</span> <span class="operator">=</span> <span class="name">Calculator</span>.<span class="name">NO_OPERATOR</span>; this.<span class="name">pendingMultiplicativeOperator</span> <span class="operator">=</span> <span class="name">Calculator</span>.<span class="name">NO_OPERATOR</span>; this.<span class="name">sumInMemory</span> <span class="operator">=</span> <span class="number">0</span>; this.<span class="name">sumSoFar</span> <span class="operator">=</span> <span class="number">0</span>; this.<span class="name">factorSoFar</span> <span class="operator">=</span> <span class="number">0</span>; this.<span class="name">waitingForOperand</span> <span class="operator">=</span> <span class="number">true</span>; <span class="keyword">with</span> (<span class="name">ui</span>) { <span class="name">display</span>.<span class="name">text</span> <span class="operator">=</span> <span class="string">"0"</span>; <span class="name">zeroButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this.<span class="name">digitClicked</span>.<span class="name">bind</span>(this, <span class="number">0</span>)); <span class="name">oneButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this.<span class="name">digitClicked</span>.<span class="name">bind</span>(this, <span class="number">1</span>)); <span class="name">twoButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this.<span class="name">digitClicked</span>.<span class="name">bind</span>(this, <span class="number">2</span>)); <span class="name">threeButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this.<span class="name">digitClicked</span>.<span class="name">bind</span>(this, <span class="number">3</span>)); <span class="name">fourButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this.<span class="name">digitClicked</span>.<span class="name">bind</span>(this, <span class="number">4</span>)); <span class="name">fiveButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this.<span class="name">digitClicked</span>.<span class="name">bind</span>(this, <span class="number">5</span>)); <span class="name">sixButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this.<span class="name">digitClicked</span>.<span class="name">bind</span>(this, <span class="number">6</span>)); <span class="name">sevenButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this.<span class="name">digitClicked</span>.<span class="name">bind</span>(this, <span class="number">7</span>)); <span class="name">eightButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this.<span class="name">digitClicked</span>.<span class="name">bind</span>(this, <span class="number">8</span>)); <span class="name">nineButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this.<span class="name">digitClicked</span>.<span class="name">bind</span>(this, <span class="number">9</span>)); <span class="name">pointButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this, <span class="string">"pointClicked"</span>); <span class="name">changeSignButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this, <span class="string">"changeSignClicked"</span>); <span class="name">backspaceButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this, <span class="string">"backspaceClicked"</span>); <span class="name">clearButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this, <span class="string">"clear"</span>); <span class="name">clearAllButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this, <span class="string">"clearAll"</span>); <span class="name">clearMemoryButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this, <span class="string">"clearMemory"</span>); <span class="name">readMemoryButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this, <span class="string">"readMemory"</span>); <span class="name">setMemoryButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this, <span class="string">"setMemory"</span>); <span class="name">addToMemoryButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this, <span class="string">"addToMemory"</span>); <span class="name">divisionButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this.<span class="name">multiplicativeOperatorClicked</span>.<span class="name">bind</span>(this, <span class="name">Calculator</span>.<span class="name">DIVISION_OPERATOR</span>)); <span class="name">timesButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this.<span class="name">multiplicativeOperatorClicked</span>.<span class="name">bind</span>(this, <span class="name">Calculator</span>.<span class="name">TIMES_OPERATOR</span>)); <span class="name">minusButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this.<span class="name">additiveOperatorClicked</span>.<span class="name">bind</span>(this, <span class="name">Calculator</span>.<span class="name">MINUS_OPERATOR</span>)); <span class="name">plusButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this.<span class="name">additiveOperatorClicked</span>.<span class="name">bind</span>(this, <span class="name">Calculator</span>.<span class="name">PLUS_OPERATOR</span>)); <span class="name">squareRootButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this.<span class="name">unaryOperatorClicked</span>.<span class="name">bind</span>(this, <span class="name">Calculator</span>.<span class="name">SQUARE_OPERATOR</span>)); <span class="name">powerButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this.<span class="name">unaryOperatorClicked</span>.<span class="name">bind</span>(this, <span class="name">Calculator</span>.<span class="name">POWER_OPERATOR</span>)); <span class="name">reciprocalButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this.<span class="name">unaryOperatorClicked</span>.<span class="name">bind</span>(this, <span class="name">Calculator</span>.<span class="name">RECIPROCAL_OPERATOR</span>)); <span class="name">equalButton</span>.<span class="name">clicked</span>.<span class="name">connect</span>(this, <span class="string">"equalClicked"</span>); } }</pre> <p>A <tt>Calculator</tt> object is just a plain script object; it is not a widget. Instead, it stores a reference to the calculator form (the widget) in an instance variable, <tt>ui</tt>. The calculator script functions can access components of the form by referring to the proper children of the <tt>ui</tt> member.</p> <pre class="js"> <span class="name">Calculator</span>.<span class="name">prototype</span>.<span class="name">digitClicked</span> <span class="operator">=</span> <span class="keyword">function</span>(<span class="name">digitValue</span>) { <span class="keyword">if</span> ((<span class="name">digitValue</span> <span class="operator">==</span> <span class="number">0</span>) <span class="operator">&&</span> (this.<span class="name">ui</span>.<span class="name">display</span>.<span class="name">text</span> <span class="operator">==</span> <span class="string">"0"</span>)) <span class="keyword">return</span>; <span class="keyword">if</span> (this.<span class="name">waitingForOperand</span>) { this.<span class="name">ui</span>.<span class="name">display</span>.<span class="name">clear</span>(); this.<span class="name">waitingForOperand</span> <span class="operator">=</span> <span class="number">false</span>; } this.<span class="name">ui</span>.<span class="name">display</span>.<span class="name">text</span> <span class="operator">+=</span> <span class="name">digitValue</span>; }</pre> <p>The digitClicked() function is called when a digit button is clicked, with the input digit as argument.</p> <pre class="js"> <span class="name">Calculator</span>.<span class="name">prototype</span>.<span class="name">changeSignClicked</span> <span class="operator">=</span> <span class="keyword">function</span>() { var <span class="name">text</span> = this.<span class="name">ui</span>.<span class="name">display</span>.<span class="name">text</span>; var <span class="name">value</span> = <span class="name">text</span> <span class="operator">-</span> <span class="number">0</span>; <span class="keyword">if</span> (<span class="name">value</span> <span class="operator">></span> <span class="number">0</span>) { <span class="name">text</span> <span class="operator">=</span> <span class="string">"-"</span> <span class="operator">+</span> <span class="name">text</span>; } else <span class="keyword">if</span> (<span class="name">value</span> <span class="operator"><</span> <span class="number">0</span>) { <span class="name">text</span> <span class="operator">=</span> <span class="name">text</span>.<span class="name">slice</span>(<span class="number">1</span>); } this.<span class="name">ui</span>.<span class="name">display</span>.<span class="name">text</span> <span class="operator">=</span> <span class="name">text</span>; }</pre> <p>The changeSign() function shows how we retrieve the text property of the calculator's display, change it appropriately, and write back the new value.</p> </div> <!-- @@@script/calculator --> </div> </div> </div> <div class="ft"> <span></span> </div> </div> <div class="footer"> <p> <acronym title="Copyright">©</acronym> 2015 The Qt Company Ltd. 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