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<td width="1">&nbsp;&nbsp;</td><td class="postheader" valign="center"><a href="index.html"><font color="#004faf">Home</font></a>&nbsp;&middot; <a href="classes.html"><font color="#004faf">All&nbsp;Classes</font></a>&nbsp;&middot; <a href="functions.html"><font color="#004faf">All&nbsp;Functions</font></a>&nbsp;&middot; <a href="overviews.html"><font color="#004faf">Overviews</font></a></td></tr></table><h1 class="title">QtScript Calculator Example<br /><span class="subtitle"></span>
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<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 this simple <a href="qtscript.html">QtScript</a> example, we show how to implement the functionality of a calculator widget.</p>
<p align="center"><img src="images/qtscript-calculator-example.png" /></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>     QScriptEngine engine;
     QString scriptFileName(&quot;:/calculator.js&quot;);
     QFile scriptFile(scriptFileName);
     scriptFile.open(QIODevice::ReadOnly);
     engine.evaluate(scriptFile.readAll(), scriptFileName);
     scriptFile.close();</pre>
</li>
<li>Create a widget from the UI file using <a href="quiloader.html">QUiLoader</a>.<pre>     QUiLoader loader;
     QFile uiFile(&quot;:/calculator.ui&quot;);
     uiFile.open(QIODevice::ReadOnly);
     QWidget *ui = loader.load(&amp;uiFile);
     uiFile.close();</pre>
</li>
<li>Call the Calculator constructor function to create a new <tt>Calculator</tt> script object, passing the widget as argument.<pre>     QScriptValue ctor = engine.evaluate(&quot;Calculator&quot;);
     QScriptValue scriptUi = engine.newQObject(ui, QScriptEngine::ScriptOwnership);
     QScriptValue calc = ctor.construct(QScriptValueList() &lt;&lt; scriptUi);</pre>
</li>
<li>Show the widget and start the application event loop.<pre>     ui-&gt;show();
     return app.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> function Calculator(ui)
 {
     this.ui = ui;

     this.pendingAdditiveOperator = Calculator.NO_OPERATOR;
     this.pendingMultiplicativeOperator = Calculator.NO_OPERATOR;
     this.sumInMemory = 0;
     this.sumSoFar = 0;
     this.factorSoFar = 0;
     this.waitingForOperand = true;

     with (ui) {
         display.text = &quot;0&quot;;

         zeroButton.clicked.connect(this.digitClicked.bind(this, 0));
         oneButton.clicked.connect(this.digitClicked.bind(this, 1));
         twoButton.clicked.connect(this.digitClicked.bind(this, 2));
         threeButton.clicked.connect(this.digitClicked.bind(this, 3));
         fourButton.clicked.connect(this.digitClicked.bind(this, 4));
         fiveButton.clicked.connect(this.digitClicked.bind(this, 5));
         sixButton.clicked.connect(this.digitClicked.bind(this, 6));
         sevenButton.clicked.connect(this.digitClicked.bind(this, 7));
         eightButton.clicked.connect(this.digitClicked.bind(this, 8));
         nineButton.clicked.connect(this.digitClicked.bind(this, 9));

         pointButton.clicked.connect(this, &quot;pointClicked&quot;);
         changeSignButton.clicked.connect(this, &quot;changeSignClicked&quot;);

         backspaceButton.clicked.connect(this, &quot;backspaceClicked&quot;);
         clearButton.clicked.connect(this, &quot;clear&quot;);
         clearAllButton.clicked.connect(this, &quot;clearAll&quot;);

         clearMemoryButton.clicked.connect(this, &quot;clearMemory&quot;);
         readMemoryButton.clicked.connect(this, &quot;readMemory&quot;);
         setMemoryButton.clicked.connect(this, &quot;setMemory&quot;);
         addToMemoryButton.clicked.connect(this, &quot;addToMemory&quot;);

         divisionButton.clicked.connect(this.multiplicativeOperatorClicked.bind(this, Calculator.DIVISION_OPERATOR));
         timesButton.clicked.connect(this.multiplicativeOperatorClicked.bind(this, Calculator.TIMES_OPERATOR));
         minusButton.clicked.connect(this.additiveOperatorClicked.bind(this, Calculator.MINUS_OPERATOR));
         plusButton.clicked.connect(this.additiveOperatorClicked.bind(this, Calculator.PLUS_OPERATOR));

         squareRootButton.clicked.connect(this.unaryOperatorClicked.bind(this, Calculator.SQUARE_OPERATOR));
         powerButton.clicked.connect(this.unaryOperatorClicked.bind(this, Calculator.POWER_OPERATOR));
         reciprocalButton.clicked.connect(this.unaryOperatorClicked.bind(this, Calculator.RECIPROCAL_OPERATOR));
         equalButton.clicked.connect(this, &quot;equalClicked&quot;);
     }
 }</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> Calculator.prototype.digitClicked = function(digitValue)
 {
     if ((digitValue == 0) &amp;&amp; (this.ui.display.text == &quot;0&quot;))
         return;
     if (this.waitingForOperand) {
         this.ui.display.clear();
         this.waitingForOperand = false;
     }
     this.ui.display.text += digitValue;
 }</pre>
<p>The digitClicked() function is called when a digit button is clicked, with the input digit as argument.</p>
<pre> Calculator.prototype.changeSignClicked = function()
 {
     var text = this.ui.display.text;
     var value = text - 0;

     if (value &gt; 0) {
         text = &quot;-&quot; + text;
     } else if (value &lt; 0) {
         text = text.slice(1);
     }
     this.ui.display.text = text;
 }</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>
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