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<li>Qt 5.3</li>
<li><a href="qtxmlpatterns-index.html">Qt XML Patterns</a></li>
<li>Recipes Example</li>
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Qt 5.3.2 Reference Documentation</li>
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<h3><a name="toc">Contents</a></h3>
<ul>
<li class="level1"><a href="#introduction">Introduction</a></li>
<li class="level2"><a href="#the-user-interface">The User Interface</a></li>
<li class="level2"><a href="#running-your-own-xqueries">Running your own XQueries</a></li>
<li class="level1"><a href="#code-walk-through">Code Walk-Through</a></li>
<li class="level2"><a href="#the-ui-class-querymainwindow">The UI Class: QueryMainWindow</a></li>
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<h1 class="title">Recipes Example</h1>
<span class="subtitle"></span>
<!-- $$$xmlpatterns/recipes-description -->
<div class="descr"> <a name="details"></a>
<p>The Recipes example shows how to use Qt XML Patterns to query XML data loaded from a file.</p>
<a name="introduction"></a>
<h2>Introduction</h2>
<p>In this case, the XML data represents a cookbook, <tt>cookbook.xml</tt>, which contains <tt><cookbook></tt> as its document element, which in turn contains a sequence of <tt><recipe></tt> elements. This XML data is searched using queries stored in <a href="xmlprocessing.html">XQuery</a> files (<tt>*.xq</tt>).</p>
<a name="the-user-interface"></a>
<h3>The User Interface</h3>
<p>The UI for this example was created using Qt Designer:</p>
<p class="centerAlign"><img src="images/recipes-example.png" alt="" /></p><p>The UI consists of three group boxes arranged vertically. The top one contains a text viewer that displays the XML text from the cookbook file. The middle group box contains a combo box for choosing the <a href="xquery-introduction.html">XQuery</a> to run and a text viewer for displaying the text of the selected <a href="xmlprocessing.html">XQuery</a>. The <tt>.xq</tt> files in the file list above are shown in the combo box menu. Choosing an <a href="xmlprocessing.html">XQuery</a> loads, parses, and runs the selected <a href="xmlprocessing.html">XQuery</a>. The query result is shown in the bottom group box's text viewer.</p>
<a name="running-your-own-xqueries"></a>
<h3>Running your own XQueries</h3>
<p>You can write your own <a href="xmlprocessing.html">XQuery</a> files and run them in the example program. The file <tt>xmlpatterns/recipes/recipes.qrc</tt> is the resource file for this example. It is used in <tt>main.cpp</tt> (<tt>Q_INIT_RESOURCE(recipes);</tt>). It lists the <a href="xmlprocessing.html">XQuery</a> files (<tt>.xq</tt>) that can be selected in the combobox.</p>
<pre class="qml"><!DOCTYPE RCC><RCC version="1.0">
<qresource>
<file>files/cookbook.xml</file>
<file>files/allRecipes.xq</file>
<file>files/liquidIngredientsInSoup.xq</file>
<file>files/mushroomSoup.xq</file>
<file>files/preparationLessThan30.xq</file>
<file>files/preparationTimes.xq</file>
</qresource>
</RCC></pre>
<p>To add your own queries to the example's combobox, store your <tt>.xq</tt> files in the <tt>examples/xmlpatterns/recipes/files</tt> directory and add them to <tt>recipes.qrc</tt> as shown above.</p>
<a name="code-walk-through"></a>
<h2>Code Walk-Through</h2>
<p>The example's main() function creates the standard instance of QApplication. Then it creates an instance of the UI class, shows it, and starts the Qt event loop:</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>)
{
Q_INIT_RESOURCE(recipes);
<span class="type">QApplication</span> app(argc<span class="operator">,</span> argv);
QueryMainWindow<span class="operator">*</span> <span class="keyword">const</span> queryWindow <span class="operator">=</span> <span class="keyword">new</span> QueryMainWindow;
queryWindow<span class="operator">-</span><span class="operator">></span>show();
<span class="keyword">return</span> app<span class="operator">.</span>exec();
}</pre>
<a name="the-ui-class-querymainwindow"></a>
<h3>The UI Class: QueryMainWindow</h3>
<p>The example's UI is a conventional Qt GUI application inheriting QMainWindow and the class generated by Qt Designer:</p>
<pre class="cpp"><span class="keyword">class</span> QueryMainWindow : <span class="keyword">public</span> <span class="type">QMainWindow</span><span class="operator">,</span>
<span class="keyword">private</span> Ui<span class="operator">::</span>QueryWidget
{
Q_OBJECT
<span class="keyword">public</span>:
QueryMainWindow();
<span class="keyword">public</span> <span class="keyword">slots</span>:
<span class="type">void</span> displayQuery(<span class="type">int</span> index);
<span class="keyword">private</span>:
<span class="type">QComboBox</span><span class="operator">*</span> ui_defaultQueries;
<span class="type">void</span> evaluate(<span class="keyword">const</span> <span class="type">QString</span> <span class="operator">&</span>str);
<span class="type">void</span> loadInputFile();
};</pre>
<p>The constructor finds the window's combo box child widget and connects its currentIndexChanged() signal to the window's <tt>displayQuery()</tt> slot. It then calls <tt>loadInputFile()</tt> to load <tt>cookbook.xml</tt> and display its contents in the top group box's text viewer . Finally, it finds the <a href="xmlprocessing.html">XQuery</a> files (<tt>.xq</tt>) and adds each one to the combo box menu.</p>
<pre class="cpp">QueryMainWindow<span class="operator">::</span>QueryMainWindow() : ui_defaultQueries(<span class="number">0</span>)
{
setupUi(<span class="keyword">this</span>);
<span class="keyword">new</span> XmlSyntaxHighlighter(findChild<span class="operator"><</span><span class="type">QTextEdit</span><span class="operator">*</span><span class="operator">></span>(<span class="string">"inputTextEdit"</span>)<span class="operator">-</span><span class="operator">></span>document());
<span class="keyword">new</span> XmlSyntaxHighlighter(findChild<span class="operator"><</span><span class="type">QTextEdit</span><span class="operator">*</span><span class="operator">></span>(<span class="string">"outputTextEdit"</span>)<span class="operator">-</span><span class="operator">></span>document());
ui_defaultQueries <span class="operator">=</span> findChild<span class="operator"><</span><span class="type">QComboBox</span><span class="operator">*</span><span class="operator">></span>(<span class="string">"defaultQueries"</span>);
<span class="type">QMetaObject</span><span class="operator">::</span>connectSlotsByName(<span class="keyword">this</span>);
connect(ui_defaultQueries<span class="operator">,</span> SIGNAL(currentIndexChanged(<span class="type">int</span>))<span class="operator">,</span> SLOT(displayQuery(<span class="type">int</span>)));
loadInputFile();
<span class="keyword">const</span> <span class="type">QStringList</span> queries(<span class="type">QDir</span>(<span class="string">":/files/"</span><span class="operator">,</span> <span class="string">"*.xq"</span>)<span class="operator">.</span>entryList());
<span class="type">int</span> len <span class="operator">=</span> queries<span class="operator">.</span>count();
<span class="keyword">for</span>(<span class="type">int</span> i <span class="operator">=</span> <span class="number">0</span>; i <span class="operator"><</span> len; <span class="operator">+</span><span class="operator">+</span>i)
ui_defaultQueries<span class="operator">-</span><span class="operator">></span>addItem(queries<span class="operator">.</span>at(i));
<span class="keyword">if</span> (len <span class="operator">></span> <span class="number">0</span>)
displayQuery(<span class="number">0</span>);
}</pre>
<p>The work is done in the <a href="#displayquery-slot">displayQuery()</a> slot and the <a href="#evaluate-function">evaluate()</a> function it calls. <a href="#displayquery-slot">displayQuery()</a> loads and displays the selected query file and passes the <a href="xmlprocessing.html">XQuery</a> text to <a href="#evaluate-function">evaluate()</a>.</p>
<a name="displayquery-slot"></a><pre class="cpp"><span class="type">void</span> QueryMainWindow<span class="operator">::</span>displayQuery(<span class="type">int</span> index)
{
<span class="type">QFile</span> queryFile(<span class="type">QString</span>(<span class="string">":files/"</span>) <span class="operator">+</span> ui_defaultQueries<span class="operator">-</span><span class="operator">></span>itemText(index));
queryFile<span class="operator">.</span>open(<span class="type">QIODevice</span><span class="operator">::</span>ReadOnly);
<span class="keyword">const</span> <span class="type">QString</span> query(<span class="type">QString</span><span class="operator">::</span>fromLatin1(queryFile<span class="operator">.</span>readAll()));
findChild<span class="operator"><</span><span class="type">QTextEdit</span><span class="operator">*</span><span class="operator">></span>(<span class="string">"queryTextEdit"</span>)<span class="operator">-</span><span class="operator">></span>setPlainText(query);
evaluate(query);
}</pre>
<p><a href="#evaluate-function">evaluate()</a> demonstrates the standard Qt XML Patterns usage pattern. First, an instance of <a href="qxmlquery.html">QXmlQuery</a> is created (<tt>query</tt>). The <tt>query's</tt> <a href="qxmlquery.html#bindVariable">bindVariable()</a> function is then called to bind the <tt>cookbook.xml</tt> file to the <a href="xmlprocessing.html">XQuery</a> variable <tt>inputDocument</tt>. <i>After</i> the variable is bound, <a href="qxmlquery.html#setQuery">setQuery()</a> is called to pass the <a href="xmlprocessing.html">XQuery</a> text to the <tt>query</tt>.</p>
<p><b>Note: </b><a href="qxmlquery.html#setQuery">setQuery()</a> must be called <i>after</i> <a href="qxmlquery.html#bindVariable">bindVariable()</a>.</p><p>Passing the <a href="xmlprocessing.html">XQuery</a> to <a href="qxmlquery.html#setQuery">setQuery()</a> causes Qt XML Patterns to parse the <a href="xmlprocessing.html">XQuery</a>. <a href="qxmlquery.html#isValid">QXmlQuery::isValid</a>() is called to ensure that the <a href="xmlprocessing.html">XQuery</a> was correctly parsed.</p>
<a name="evaluate-function"></a><pre class="cpp"><span class="type">void</span> QueryMainWindow<span class="operator">::</span>evaluate(<span class="keyword">const</span> <span class="type">QString</span> <span class="operator">&</span>str)
{
<span class="type">QFile</span> sourceDocument;
sourceDocument<span class="operator">.</span>setFileName(<span class="string">":/files/cookbook.xml"</span>);
sourceDocument<span class="operator">.</span>open(<span class="type">QIODevice</span><span class="operator">::</span>ReadOnly);
<span class="type">QByteArray</span> outArray;
<span class="type">QBuffer</span> buffer(<span class="operator">&</span>outArray);
buffer<span class="operator">.</span>open(<span class="type">QIODevice</span><span class="operator">::</span>ReadWrite);
<span class="type"><a href="qxmlquery.html">QXmlQuery</a></span> query;
query<span class="operator">.</span>bindVariable(<span class="string">"inputDocument"</span><span class="operator">,</span> <span class="operator">&</span>sourceDocument);
query<span class="operator">.</span>setQuery(str);
<span class="keyword">if</span> (<span class="operator">!</span>query<span class="operator">.</span>isValid())
<span class="keyword">return</span>;
<span class="type"><a href="qxmlformatter.html">QXmlFormatter</a></span> formatter(query<span class="operator">,</span> <span class="operator">&</span>buffer);
<span class="keyword">if</span> (<span class="operator">!</span>query<span class="operator">.</span>evaluateTo(<span class="operator">&</span>formatter))
<span class="keyword">return</span>;
buffer<span class="operator">.</span>close();
findChild<span class="operator"><</span><span class="type">QTextEdit</span><span class="operator">*</span><span class="operator">></span>(<span class="string">"outputTextEdit"</span>)<span class="operator">-</span><span class="operator">></span>setPlainText(<span class="type">QString</span><span class="operator">::</span>fromUtf8(outArray<span class="operator">.</span>constData()));
}</pre>
<p>If the <a href="xmlprocessing.html">XQuery</a> is valid, an instance of <a href="qxmlformatter.html">QXmlFormatter</a> is created to format the query result as XML into a QBuffer. To evaluate the <a href="xmlprocessing.html">XQuery</a>, an overload of <a href="qxmlquery.html#evaluateTo">evaluateTo()</a> is called that takes a <a href="qabstractxmlreceiver.html">QAbstractXmlReceiver</a> for its output (<a href="qxmlformatter.html">QXmlFormatter</a> inherits <a href="qabstractxmlreceiver.html">QAbstractXmlReceiver</a>). Finally, the formatted XML result is displayed in the UI's bottom text view.</p>
<p><b>Note: </b>Each <a href="xmlprocessing.html">XQuery</a> <tt>.xq</tt> file must declare the <tt>$inputDocument</tt> variable to represent the <tt>cookbook.xml</tt> document:</p><pre class="cpp">(: All ingredients <span class="keyword">for</span> Mushroom Soup<span class="operator">.</span> :)
declare variable $inputDocument external;
doc($inputDocument)<span class="operator">/</span>cookbook<span class="operator">/</span>recipe<span class="operator">[</span>@xml:id <span class="operator">=</span> <span class="string">"MushroomSoup"</span><span class="operator">]</span><span class="operator">/</span>ingredient<span class="operator">/</span>
<span class="operator"><</span>p<span class="operator">></span>{@name<span class="operator">,</span> @quantity}<span class="operator"><</span><span class="operator">/</span>p<span class="operator">></span></pre>
<p><b>Note: </b>If you add add your own query.xq files, you must declare the <tt>$inputDocument</tt> and use it as shown above.</p><p>Files:</p>
<ul>
<li><a href="qtxmlpatterns-xmlpatterns-recipes-querymainwindow-cpp.html">xmlpatterns/recipes/querymainwindow.cpp</a></li>
<li><a href="qtxmlpatterns-xmlpatterns-recipes-querymainwindow-h.html">xmlpatterns/recipes/querymainwindow.h</a></li>
<li><a href="qtxmlpatterns-xmlpatterns-recipes-files-allrecipes-xq.html">xmlpatterns/recipes/files/allRecipes.xq</a></li>
<li><a href="qtxmlpatterns-xmlpatterns-recipes-files-cookbook-xml.html">xmlpatterns/recipes/files/cookbook.xml</a></li>
<li><a href="qtxmlpatterns-xmlpatterns-recipes-files-liquidingredientsinsoup-xq.html">xmlpatterns/recipes/files/liquidIngredientsInSoup.xq</a></li>
<li><a href="qtxmlpatterns-xmlpatterns-recipes-files-mushroomsoup-xq.html">xmlpatterns/recipes/files/mushroomSoup.xq</a></li>
<li><a href="qtxmlpatterns-xmlpatterns-recipes-files-preparationlessthan30-xq.html">xmlpatterns/recipes/files/preparationLessThan30.xq</a></li>
<li><a href="qtxmlpatterns-xmlpatterns-recipes-files-preparationtimes-xq.html">xmlpatterns/recipes/files/preparationTimes.xq</a></li>
<li><a href="qtxmlpatterns-xmlpatterns-recipes-forms-querywidget-ui.html">xmlpatterns/recipes/forms/querywidget.ui</a></li>
<li><a href="qtxmlpatterns-xmlpatterns-recipes-forms-querywidget-mobiles-ui.html">xmlpatterns/recipes/forms/querywidget_mobiles.ui</a></li>
<li><a href="qtxmlpatterns-xmlpatterns-recipes-main-cpp.html">xmlpatterns/recipes/main.cpp</a></li>
<li><a href="qtxmlpatterns-xmlpatterns-recipes-recipes-pro.html">xmlpatterns/recipes/recipes.pro</a></li>
<li><a href="qtxmlpatterns-xmlpatterns-recipes-recipes-qrc.html">xmlpatterns/recipes/recipes.qrc</a></li>
</ul>
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