/usr/share/qt5/doc/qtquick/qtquick-modelviewsdata-cppmodels.html is in qtdeclarative5-doc-html 5.9.5-0ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 | <?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html>
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<!-- cppmodels.qdoc -->
<title>Using C++ Models with Qt Quick Views | Qt Quick 5.9</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 5.9</td><td ><a href="qtquick-index.html">Qt Quick</a></td><td >Using C++ Models with Qt Quick Views</td></tr></table><table class="buildversion"><tr>
<td id="buildversion" width="100%" align="right">Qt 5.9.5 Reference Documentation</td>
</tr></table>
</div>
</div>
<div class="content">
<div class="line">
<div class="content mainContent">
<div class="sidebar">
<div class="toc">
<h3><a name="toc">Contents</a></h3>
<ul>
<li class="level1"><a href="#data-provided-in-a-custom-c-model">Data Provided In A Custom C++ Model</a></li>
<li class="level2"><a href="#qstringlist-based-model">QStringList-based Model</a></li>
<li class="level2"><a href="#qvariantlist-based-model">QVariantList-based Model</a></li>
<li class="level2"><a href="#qobjectlist-based-model">QObjectList-based Model</a></li>
<li class="level2"><a href="#qabstractitemmodel-subclass">QAbstractItemModel Subclass</a></li>
<li class="level2"><a href="#sql-models">SQL Models</a></li>
<li class="level2"><a href="#exposing-c-data-models-to-qml">Exposing C++ Data Models to QML</a></li>
</ul>
</div>
<div class="sidebar-content" id="sidebar-content"></div></div>
<h1 class="title">Using C++ Models with Qt Quick Views</h1>
<span class="subtitle"></span>
<!-- $$$qtquick-modelviewsdata-cppmodels.html-description -->
<div class="descr"> <a name="details"></a>
<a name="data-provided-in-a-custom-c-model"></a>
<h2 id="data-provided-in-a-custom-c-model">Data Provided In A Custom C++ Model</h2>
<p>Models can be defined in C++ and then made available to QML. This is useful for exposing existing C++ data models or otherwise complex datasets to QML.</p>
<p>A C++ model class can be defined as a <a href="../qtcore/qstringlist.html">QStringList</a>, a <a href="../qtcore/qvariant.html#QVariantList-typedef">QVariantList</a>, a <a href="../qtcore/qobject.html#QObjectList-typedef">QObjectList</a> or a <a href="../qtcore/qabstractitemmodel.html">QAbstractItemModel</a>. The first three are useful for exposing simpler datasets, while <a href="../qtcore/qabstractitemmodel.html">QAbstractItemModel</a> provides a more flexible solution for more complex models.</p>
<p>For a video tutorial that takes you through the whole process of exposing a C++ model to QML, see the <a href="https://youtu.be/9BcAYDlpuT8">Using C++ Models in QML Tutorial</a>.</p>
<a name="qstringlist-based-model"></a>
<h3 >QStringList-based Model</h3>
<p>A model may be a simple <a href="../qtcore/qstringlist.html">QStringList</a>, which provides the contents of the list via the <i>modelData</i> role.</p>
<p>Here is a <a href="qml-qtquick-listview.html">ListView</a> with a delegate that references its model item's value using the <code>modelData</code> role:</p>
<pre class="qml">
<span class="type"><a href="qml-qtquick-listview.html">ListView</a></span> {
<span class="name">width</span>: <span class="number">100</span>; <span class="name">height</span>: <span class="number">100</span>
<span class="name">model</span>: <span class="name">myModel</span>
<span class="name">delegate</span>: <span class="name">Rectangle</span> {
<span class="name">height</span>: <span class="number">25</span>
<span class="name">width</span>: <span class="number">100</span>
<span class="type"><a href="qml-qtquick-text.html">Text</a></span> { <span class="name">text</span>: <span class="name">modelData</span> }
}
}
</pre>
<p>A Qt application can load this QML document and set the value of <code>myModel</code> to a <a href="../qtcore/qstringlist.html">QStringList</a>:</p>
<pre class="cpp">
<span class="type"><a href="../qtcore/qstringlist.html">QStringList</a></span> dataList;
dataList<span class="operator">.</span>append(<span class="string">"Item 1"</span>);
dataList<span class="operator">.</span>append(<span class="string">"Item 2"</span>);
dataList<span class="operator">.</span>append(<span class="string">"Item 3"</span>);
dataList<span class="operator">.</span>append(<span class="string">"Item 4"</span>);
<span class="type"><a href="qquickview.html">QQuickView</a></span> view;
<span class="type">QQmlContext</span> <span class="operator">*</span>ctxt <span class="operator">=</span> view<span class="operator">.</span>rootContext();
ctxt<span class="operator">-</span><span class="operator">></span>setContextProperty(<span class="string">"myModel"</span><span class="operator">,</span> <span class="type"><a href="../qtcore/qvariant.html">QVariant</a></span><span class="operator">::</span>fromValue(dataList));
</pre>
<p>The complete source code for this example is available in <a href="qtquick-models-stringlistmodel-example.html">examples/quick/models/stringlistmodel</a> within the Qt install directory.</p>
<p><b>Note: </b>There is no way for the view to know that the contents of a <a href="../qtcore/qstringlist.html">QStringList</a> have changed. If the <a href="../qtcore/qstringlist.html">QStringList</a> changes, it will be necessary to reset the model by calling QQmlContext::setContextProperty() again.</p><a name="qvariantlist-based-model"></a>
<h3 >QVariantList-based Model</h3>
<p>A model may be a single <a href="../qtcore/qvariant.html#QVariantList-typedef">QVariantList</a>, which provides the contents of the list via the <i>modelData</i> role.</p>
<p>The API works just like with <a href="../qtcore/qstringlist.html">QStringList</a>, as shown in the previous section.</p>
<p><b>Note: </b>There is no way for the view to know that the contents of a <a href="../qtcore/qvariant.html#QVariantList-typedef">QVariantList</a> have changed. If the <a href="../qtcore/qvariant.html#QVariantList-typedef">QVariantList</a> changes, it will be necessary to reset the model.</p><a name="qobjectlist-based-model"></a>
<h3 >QObjectList-based Model</h3>
<p>A list of <a href="../qtcore/qobject.html">QObject</a>* values can also be used as a model. A <a href="../qtcore/qlist.html">QList</a><<a href="../qtcore/qobject.html">QObject</a>*> provides the properties of the objects in the list as roles.</p>
<p>The following application creates a <code>DataObject</code> class with <a href="../qtcore/qobject.html#Q_PROPERTY">Q_PROPERTY</a> values that will be accessible as named roles when a <a href="../qtcore/qlist.html">QList</a><DataObject*> is exposed to QML:</p>
<pre class="cpp">
<span class="keyword">class</span> DataObject : <span class="keyword">public</span> <span class="type"><a href="../qtcore/qobject.html">QObject</a></span>
{
Q_OBJECT
Q_PROPERTY(<span class="type"><a href="../qtcore/qstring.html">QString</a></span> name READ name WRITE setName NOTIFY nameChanged)
Q_PROPERTY(<span class="type"><a href="../qtcore/qstring.html">QString</a></span> color READ color WRITE setColor NOTIFY colorChanged)
...
};
<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="../qtgui/qguiapplication.html">QGuiApplication</a></span> app(argc<span class="operator">,</span> argv);
<span class="type"><a href="../qtcore/qlist.html">QList</a></span><span class="operator"><</span><span class="type"><a href="../qtcore/qobject.html">QObject</a></span><span class="operator">*</span><span class="operator">></span> dataList;
dataList<span class="operator">.</span>append(<span class="keyword">new</span> DataObject(<span class="string">"Item 1"</span><span class="operator">,</span> <span class="string">"red"</span>));
dataList<span class="operator">.</span>append(<span class="keyword">new</span> DataObject(<span class="string">"Item 2"</span><span class="operator">,</span> <span class="string">"green"</span>));
dataList<span class="operator">.</span>append(<span class="keyword">new</span> DataObject(<span class="string">"Item 3"</span><span class="operator">,</span> <span class="string">"blue"</span>));
dataList<span class="operator">.</span>append(<span class="keyword">new</span> DataObject(<span class="string">"Item 4"</span><span class="operator">,</span> <span class="string">"yellow"</span>));
<span class="type"><a href="qquickview.html">QQuickView</a></span> view;
view<span class="operator">.</span>setResizeMode(<span class="type"><a href="qquickview.html">QQuickView</a></span><span class="operator">::</span>SizeRootObjectToView);
<span class="type">QQmlContext</span> <span class="operator">*</span>ctxt <span class="operator">=</span> view<span class="operator">.</span>rootContext();
ctxt<span class="operator">-</span><span class="operator">></span>setContextProperty(<span class="string">"myModel"</span><span class="operator">,</span> <span class="type"><a href="../qtcore/qvariant.html">QVariant</a></span><span class="operator">::</span>fromValue(dataList));
...
</pre>
<p>The <a href="../qtcore/qobject.html">QObject</a>* is available as the <code>modelData</code> property. As a convenience, the properties of the object are also made available directly in the delegate's context. Here, <code>view.qml</code> references the <code>DataModel</code> properties in the <a href="qml-qtquick-listview.html">ListView</a> delegate:</p>
<pre class="qml">
<span class="type"><a href="qml-qtquick-listview.html">ListView</a></span> {
<span class="name">width</span>: <span class="number">100</span>; <span class="name">height</span>: <span class="number">100</span>
<span class="name">model</span>: <span class="name">myModel</span>
<span class="name">delegate</span>: <span class="name">Rectangle</span> {
<span class="name">height</span>: <span class="number">25</span>
<span class="name">width</span>: <span class="number">100</span>
<span class="name">color</span>: <span class="name">model</span>.<span class="name">modelData</span>.<span class="name">color</span>
<span class="type"><a href="qml-qtquick-text.html">Text</a></span> { <span class="name">text</span>: <span class="name">name</span> }
}
}
</pre>
<p>Note the use of <code>color</code> property with qualifier. The properties of the object are not replicated in the <code>model</code> object, as they are easily available via the <code>modelData</code> object.</p>
<p>The complete source code for this example is available in <a href="qtquick-models-objectlistmodel-example.html">examples/quick/models/objectlistmodel</a> within the Qt install directory.</p>
<p>Note: There is no way for the view to know that the contents of a <a href="../qtcore/qlist.html">QList</a> has changed. If the <a href="../qtcore/qlist.html">QList</a> changes, it is necessary to reset the model by calling QQmlContext::setContextProperty() again.</p>
<a name="qabstractitemmodel-subclass"></a>
<h3 >QAbstractItemModel Subclass</h3>
<p>A model can be defined by subclassing <a href="../qtcore/qabstractitemmodel.html">QAbstractItemModel</a>. This is the best approach if you have a more complex model that cannot be supported by the other approaches. A <a href="../qtcore/qabstractitemmodel.html">QAbstractItemModel</a> can also automatically notify a QML view when the model data changes.</p>
<p>The roles of a <a href="../qtcore/qabstractitemmodel.html">QAbstractItemModel</a> subclass can be exposed to QML by reimplementing <a href="../qtcore/qabstractitemmodel.html#roleNames">QAbstractItemModel::roleNames</a>().</p>
<p>Here is an application with a <a href="../qtcore/qabstractlistmodel.html">QAbstractListModel</a> subclass named <code>AnimalModel</code>, which exposes the <i>type</i> and <i>sizes</i> roles. It reimplements <a href="../qtcore/qabstractitemmodel.html#roleNames">QAbstractItemModel::roleNames</a>() to expose the role names, so that they can be accessed via QML:</p>
<pre class="cpp">
<span class="keyword">class</span> Animal
{
<span class="keyword">public</span>:
Animal(<span class="keyword">const</span> <span class="type"><a href="../qtcore/qstring.html">QString</a></span> <span class="operator">&</span>type<span class="operator">,</span> <span class="keyword">const</span> <span class="type"><a href="../qtcore/qstring.html">QString</a></span> <span class="operator">&</span>size);
...
};
<span class="keyword">class</span> AnimalModel : <span class="keyword">public</span> <span class="type"><a href="../qtcore/qabstractlistmodel.html">QAbstractListModel</a></span>
{
Q_OBJECT
<span class="keyword">public</span>:
<span class="keyword">enum</span> AnimalRoles {
TypeRole <span class="operator">=</span> <span class="type"><a href="../qtcore/qt.html">Qt</a></span><span class="operator">::</span>UserRole <span class="operator">+</span> <span class="number">1</span><span class="operator">,</span>
SizeRole
};
AnimalModel(<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/qhash.html">QHash</a></span><span class="operator"><</span><span class="type">int</span><span class="operator">,</span> <span class="type"><a href="../qtcore/qbytearray.html">QByteArray</a></span><span class="operator">></span> AnimalModel<span class="operator">::</span>roleNames() <span class="keyword">const</span> {
<span class="type"><a href="../qtcore/qhash.html">QHash</a></span><span class="operator"><</span><span class="type">int</span><span class="operator">,</span> <span class="type"><a href="../qtcore/qbytearray.html">QByteArray</a></span><span class="operator">></span> roles;
roles<span class="operator">[</span>TypeRole<span class="operator">]</span> <span class="operator">=</span> <span class="string">"type"</span>;
roles<span class="operator">[</span>SizeRole<span class="operator">]</span> <span class="operator">=</span> <span class="string">"size"</span>;
<span class="keyword">return</span> roles;
}
<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="../qtgui/qguiapplication.html">QGuiApplication</a></span> app(argc<span class="operator">,</span> argv);
AnimalModel model;
model<span class="operator">.</span>addAnimal(Animal(<span class="string">"Wolf"</span><span class="operator">,</span> <span class="string">"Medium"</span>));
model<span class="operator">.</span>addAnimal(Animal(<span class="string">"Polar bear"</span><span class="operator">,</span> <span class="string">"Large"</span>));
model<span class="operator">.</span>addAnimal(Animal(<span class="string">"Quoll"</span><span class="operator">,</span> <span class="string">"Small"</span>));
<span class="type"><a href="qquickview.html">QQuickView</a></span> view;
view<span class="operator">.</span>setResizeMode(<span class="type"><a href="qquickview.html">QQuickView</a></span><span class="operator">::</span>SizeRootObjectToView);
<span class="type">QQmlContext</span> <span class="operator">*</span>ctxt <span class="operator">=</span> view<span class="operator">.</span>rootContext();
ctxt<span class="operator">-</span><span class="operator">></span>setContextProperty(<span class="string">"myModel"</span><span class="operator">,</span> <span class="operator">&</span>model);
...
</pre>
<p>This model is displayed by a <a href="qml-qtquick-listview.html">ListView</a> delegate that accesses the <i>type</i> and <i>size</i> roles:</p>
<pre class="qml">
<span class="type"><a href="qml-qtquick-listview.html">ListView</a></span> {
<span class="name">width</span>: <span class="number">200</span>; <span class="name">height</span>: <span class="number">250</span>
<span class="name">model</span>: <span class="name">myModel</span>
<span class="name">delegate</span>: <span class="name">Text</span> { <span class="name">text</span>: <span class="string">"Animal: "</span> <span class="operator">+</span> <span class="name">type</span> <span class="operator">+</span> <span class="string">", "</span> <span class="operator">+</span> <span class="name">size</span> }
}
</pre>
<p>QML views are automatically updated when the model changes. Remember the model must follow the standard rules for model changes and notify the view when the model has changed by using <a href="../qtcore/qabstractitemmodel.html#dataChanged">QAbstractItemModel::dataChanged</a>(), <a href="../qtcore/qabstractitemmodel.html#beginInsertRows">QAbstractItemModel::beginInsertRows</a>(), and so on. See the <a href="../qtwidgets/model-view-programming.html#model-subclassing-reference">Model subclassing reference</a> for more information.</p>
<p>The complete source code for this example is available in <a href="qtquick-models-abstractitemmodel-example.html">examples/quick/models/abstractitemmodel</a> within the Qt install directory.</p>
<p><a href="../qtcore/qabstractitemmodel.html">QAbstractItemModel</a> presents a hierarchy of tables, but the views currently provided by QML can only display list data. In order to display the child lists of a hierarchical model, use the DelegateModel QML type, which provides the following properties and functions to be used with list models of <a href="../qtcore/qabstractitemmodel.html">QAbstractItemModel</a> type:</p>
<ul>
<li><i>hasModelChildren</i> role property to determine whether a node has child nodes.</li>
<li>DelegateModel::rootIndex allows the root node to be specified</li>
<li>DelegateModel::modelIndex() returns a <a href="../qtcore/qmodelindex.html">QModelIndex</a> which can be assigned to DelegateModel::rootIndex</li>
<li>DelegateModel::parentModelIndex() returns a <a href="../qtcore/qmodelindex.html">QModelIndex</a> which can be assigned to DelegateModel::rootIndex</li>
</ul>
<a name="sql-models"></a>
<h3 >SQL Models</h3>
<p>Qt provides C++ classes that support SQL data models. These classes work transparently on the underlying SQL data, reducing the need to run SQL queries for basic SQL operations such as create, insert, or update. For more details about these classes, see Using the SQL Model Classes.</p>
<p>Although the C++ classes provide complete feature sets to operate on SQL data, they do not provide data access to QML. So you must implement a C++ custom data model as a subclass of one of these classes, and expose it to QML either as a type or context property.</p>
<a name="read-only-data-model"></a>
<h4 >Read-only Data Model</h4>
<p>The custom model must reimplement the following methods to enable read-only access to the data from QML:</p>
<ul>
<li><a href="../qtcore/qabstractitemmodel.html#roleNames">roleNames</a>() to expose the role names to the QML frontend. For example, the following version returns the selected table's field names as role names:<pre class="cpp">
<span class="type"><a href="../qtcore/qhash.html">QHash</a></span><span class="operator"><</span><span class="type">int</span><span class="operator">,</span> <span class="type"><a href="../qtcore/qbytearray.html">QByteArray</a></span><span class="operator">></span> SqlQueryModel<span class="operator">::</span>roleNames() <span class="keyword">const</span>
{
<span class="type"><a href="../qtcore/qhash.html">QHash</a></span><span class="operator"><</span><span class="type">int</span><span class="operator">,</span> <span class="type"><a href="../qtcore/qbytearray.html">QByteArray</a></span><span class="operator">></span> roles;
<span class="comment">// record() returns an empty QSqlRecord</span>
<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> <span class="keyword">this</span><span class="operator">-</span><span class="operator">></span>record()<span class="operator">.</span>count(); i <span class="operator">+</span><span class="operator">+</span>) {
roles<span class="operator">.</span>insert(<span class="type"><a href="../qtcore/qt.html">Qt</a></span><span class="operator">::</span>UserRole <span class="operator">+</span> i <span class="operator">+</span> <span class="number">1</span><span class="operator">,</span> record()<span class="operator">.</span>fieldName(i)<span class="operator">.</span>toUtf8());
}
<span class="keyword">return</span> roles;
}
</pre>
</li>
<li>data() to expose SQL data to the QML frontend. For example, the following implementation returns data for the given model index:<pre class="cpp">
<span class="type"><a href="../qtcore/qvariant.html">QVariant</a></span> SqlQueryModel<span class="operator">::</span>data(<span class="keyword">const</span> <span class="type"><a href="../qtcore/qmodelindex.html">QModelIndex</a></span> <span class="operator">&</span>index<span class="operator">,</span> <span class="type">int</span> role) <span class="keyword">const</span>
{
<span class="type"><a href="../qtcore/qvariant.html">QVariant</a></span> value;
<span class="keyword">if</span> (index<span class="operator">.</span>isValid()) {
<span class="keyword">if</span> (role <span class="operator"><</span> <span class="type"><a href="../qtcore/qt.html">Qt</a></span><span class="operator">::</span>UserRole) {
value <span class="operator">=</span> <span class="type">QSqlQueryModel</span><span class="operator">::</span>data(index<span class="operator">,</span> role);
} <span class="keyword">else</span> {
<span class="type">int</span> columnIdx <span class="operator">=</span> role <span class="operator">-</span> <span class="type"><a href="../qtcore/qt.html">Qt</a></span><span class="operator">::</span>UserRole <span class="operator">-</span> <span class="number">1</span>;
<span class="type"><a href="../qtcore/qmodelindex.html">QModelIndex</a></span> modelIndex <span class="operator">=</span> <span class="keyword">this</span><span class="operator">-</span><span class="operator">></span>index(index<span class="operator">.</span>row()<span class="operator">,</span> columnIdx);
value <span class="operator">=</span> <span class="type">QSqlQueryModel</span><span class="operator">::</span>data(modelIndex<span class="operator">,</span> <span class="type"><a href="../qtcore/qt.html">Qt</a></span><span class="operator">::</span>DisplayRole);
}
}
<span class="keyword">return</span> value;
}
</pre>
</li>
</ul>
<p>The QSqlQueryModel class is good enough to implement a custom read-only model that represents data in an SQL database. The chat tutorial example demonstrates this very well by implementing a custom model to fetch the contact details from an SQLite database.</p>
<a name="editable-data-model"></a>
<h4 >Editable Data Model</h4>
<p>Besides the <code>roleNames()</code> and <code>data()</code>, the editable models must reimplement the setData method to save changes to existing SQL data. The following version of the method checks if the given model index is valid and the <code>role</code> is equal to <a href="../qtcore/qt.html#ItemDataRole-enum">Qt::EditRole</a>, before calling the parent class version:</p>
<pre class="cpp">
bool SqlEditableModel<span class="operator">::</span>setData(<span class="keyword">const</span> <span class="type"><a href="../qtcore/qmodelindex.html">QModelIndex</a></span> <span class="operator">&</span>item<span class="operator">,</span> <span class="keyword">const</span> <span class="type"><a href="../qtcore/qvariant.html">QVariant</a></span> <span class="operator">&</span>value<span class="operator">,</span> <span class="type">int</span> role)
{
<span class="keyword">if</span> (item<span class="operator">.</span>isValid() <span class="operator">&</span><span class="operator">&</span> role <span class="operator">=</span><span class="operator">=</span> <span class="type"><a href="../qtcore/qt.html">Qt</a></span><span class="operator">::</span>EditRole) {
<span class="type">QSqlTableModel</span><span class="operator">::</span>setData(item<span class="operator">,</span> value<span class="operator">,</span>role);
<span class="keyword">emit</span> dataChanged(item<span class="operator">,</span> item);
<span class="keyword">return</span> <span class="keyword">true</span>;
}
<span class="keyword">return</span> <span class="keyword">false</span>;
}
</pre>
<p><b>Note: </b>It is important to emit the <a href="../qtcore/qabstractitemmodel.html#dataChanged">dataChanged</a>() signal after saving the changes.</p><p>Unlike the C++ item views such as <a href="../qtwidgets/qlistview.html">QListView</a> or <a href="../qtwidgets/qtableview.html">QTableView</a>, the <code>setData()</code> method must be explicitly invoked from QML whenever appropriate. For example, on the editingFinished() or accepted() signal of TextField. Depending on the EditStrategy used by the model, the changes are either queued for submission later or submitted immediately.</p>
<p>You can also insert new data into the model by calling QSqlTableModel::insertRecord(). In the following example snippet, a QSqlRecord is populated with book details and appended to the model:</p>
<pre class="cpp">
<span class="operator">.</span><span class="operator">.</span><span class="operator">.</span>
<span class="type">QSqlRecord</span> newRecord <span class="operator">=</span> record();
newRecord<span class="operator">.</span>setValue(<span class="string">"author"</span><span class="operator">,</span> <span class="string">"John Grisham"</span>);
newRecord<span class="operator">.</span>setValue(<span class="string">"booktitle"</span><span class="operator">,</span> <span class="string">"The Litigators"</span>);
insertRecord(rowCount()<span class="operator">,</span> newRecord);
<span class="operator">.</span><span class="operator">.</span><span class="operator">.</span>
</pre>
<a name="exposing-c-data-models-to-qml"></a>
<h3 >Exposing C++ Data Models to QML</h3>
<p>The above examples use QQmlContext::setContextProperty() to set model values directly in QML components. An alternative to this is to register the C++ model class as a QML type (either directly from a C++ entry-point, or within the initialization function of a QML C++ plugin, as shown below). This would allow the model classes to be created directly as types within QML:</p>
<div class="table"><table class="generic">
<tr valign="top" class="odd"><td >C++</td><td ><pre class="cpp">
<span class="keyword">class</span> MyModelPlugin : <span class="keyword">public</span> <span class="type">QQmlExtensionPlugin</span>
{
Q_OBJECT
Q_PLUGIN_METADATA(IID <span class="string">"org.qt-project.QmlExtension.MyModel"</span> FILE <span class="string">"mymodel.json"</span>)
<span class="keyword">public</span>:
<span class="type">void</span> registerTypes(<span class="keyword">const</span> <span class="type">char</span> <span class="operator">*</span>uri)
{
qmlRegisterType<span class="operator"><</span>MyModel<span class="operator">></span>(uri<span class="operator">,</span> <span class="number">1</span><span class="operator">,</span> <span class="number">0</span><span class="operator">,</span>
<span class="string">"MyModel"</span>);
}
}
</pre>
</td></tr>
<tr valign="top" class="even"><td >QML</td><td ><pre class="qml">
<span class="type">MyModel</span> {
<span class="name">id</span>: <span class="name">myModel</span>
<span class="type">ListElement</span> { <span class="name">someProperty</span>: <span class="string">"some value"</span> }
}
</pre>
<pre class="qml">
<span class="type"><a href="qml-qtquick-listview.html">ListView</a></span> {
<span class="name">width</span>: <span class="number">200</span>; <span class="name">height</span>: <span class="number">250</span>
<span class="name">model</span>: <span class="name">myModel</span>
<span class="name">delegate</span>: <span class="name">Text</span> { <span class="name">text</span>: <span class="name">someProperty</span> }
}
</pre>
</td></tr>
</table></div>
<p>See Writing QML Extensions with C++ for details on writing QML C++ plugins.</p>
</div>
<!-- @@@qtquick-modelviewsdata-cppmodels.html -->
</div>
</div>
</div>
</div>
</div>
<div class="footer">
<p>
<acronym title="Copyright">©</acronym> 2017 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>
|