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# QForm::Loader Class Reference
[QtForm module]

The Loader class allows standalone applications dynamically create user interfaces at run-time using the information stored in .ui files or specified plugin paths. More...

    #include <QForm>

- List of all members, including inherited members

### Public Functions

- Loader ( QObject * parent = 0 )
- virtual ~Loader ()
- void addPluginPath ( const QString & path )
- QStringList availableWidgets () const
- void clearPluginPaths ()
- virtual QAction * createAction ( QObject * parent = 0, const QString & objectName = QString() )
- virtual QActionGroup * createActionGroup ( QObject * parent = 0, const QString & objectName = QString() )
- virtual QLayout * createLayout ( const QString & className, QObject * parent = 0, const QString & objectName = QString() )
- virtual QWidget * createWidget ( const QString & className, QWidget * parent = 0, const QString & objectName = QString() )
- QWidget * load ( QIODevice * device, QWidget * parent = 0 )
- QStringList pluginPaths () const

## Detailed Description

The Loader class allows standalone applications dynamically create user interfaces at run-time using the information stored in .ui files or specified plugin paths.

In addition, you can intervene the process of creating an user interface by deriving your own loader class.

If you have a custom component or application that embed Qt Designer, you can also use the QFormBuilder class provided by the QtDesigner module to create user interfaces from .ui files.

The Loader class provides a collection of functions that allows you to create widgets based on the information stored in `.ui` files (created with Qt Designer) or available in the specified plugin paths. The specified plugin paths can be retrieved using the pluginPaths() function. You can retrieve the contents of an `.ui` file using the load() function. For example:

        MyForm::MyForm(QWidget *parent)
            : QWidget(parent)
        {
            QForm::loader loader;
            QFile file(":/forms/mywidget.ui");
            file.open(QFile::ReadOnly);
            QWidget *myWidget = loader.load(&file, this);
            file.close();

            QVBoxLayout *layout = new QVBoxLayout;
            layout->addWidget(myWidget);
            setLayout(layout);
        }

By including the user interface in the form's resources (`myForm.grc`), we ensure that it will be present at run-time:

            <!DOCTYPE RCC><RCC version="1.0">
            <qresource prefix="/forms">
            <file>mywidget.ui</file>
            </qresource>
            </RCC>

The availableWidgets() function returns a QStringList with the class names of the widgets available in the specified plugin paths. You can create any of these widgets using the createWidget() function. For example:

            QForm::Loader loader;
            MyCustomWidget *myWidget;
            QWidget parent;

            QStringList availableWidgets = loader.availableWidgets();

            if (availableWidgets.contains("MyCustomWidget"))
                myWidget = qobject_cast<MyCustomWidget *>loader.createWidget("MyCustomWidget",
                                                                              parent)
            }

You can make a custom widget available to the loader using the addPluginPath() function, and you can remove all the available widgets by calling the clearPluginPaths() function.

The createAction(), createActionGroup(), createLayout() and createWidget() functions are used internally by the Loader class whenever it has to create an action, action group, layout or widget respectively. For that reason, you can subclass the Loader class and reimplement these functions to intervene the process of constructing an user interface. For example, you might want to create a list of the actions created when loading a form or creating a custom widget.

For a complete example using the Loader class, see the Calculator Builder example.

See also QForm and QFormBuilder.

## Member Function Documentation

### Loader::Loader ( QObject * parent = 0 )

Creates a form loader with the given parent.

### Loader::~Loader () `[virtual]`

Destroys the loader.

### void Loader::addPluginPath ( const QString & path )

Adds the given path to the list of paths the loader searches when locating plugins.

See also pluginPaths() and clearPluginPaths().

### QStringList Loader::availableWidgets () const

Returns a list naming the available widgets that can be built using the createWidget() function, i.e all the widgets specified within the given plugin paths.

See also pluginPaths() and createWidget().

### void Loader::clearPluginPaths ()

Clears the list of paths the loader searches when locating plugins.

See also addPluginPath() and pluginPaths().

### QAction * Loader::createAction ( QObject * parent = 0, const QString & objectName = QString() ) `[virtual]`

Creates a new action with the given parent and objectName.

The function is used internally by the Loader class whenever it has to create an action. For that reason, you can subclass the Loader class and reimplement this function to intervene the process of constructing an user interface or widget.

See also createActionGroup(), createWidget(), and load().

### QActionGroup * Loader::createActionGroup ( QObject * parent = 0, const QString & objectName = QString() ) `[virtual]`

Creates a new action group with the given parent and objectName.

The function is used internally by the Loader class whenever it has to create an action group. For that reason, you can subclass the Loader class and reimplement this function to intervene the process of constructing an user interface or widget.

See also createAction(), createWidget(), and load().

### QLayout * Loader::createLayout ( const QString & className, QObject * parent = 0, const QString & objectName = QString() ) `[virtual]`

Creates a new layout with the given parent and objectName using the class specified by className.

The function is used internally by the Loader class whenever it has to create a layout. For that reason, you can subclass the Loader class and reimplement this function to intervene the process of constructing an user interface or widget.

See also createWidget() and load().

### QWidget * Loader::createWidget ( const QString & className, QWidget * parent = 0, const QString & objectName = QString() ) `[virtual]`

Creates a new widget with the given parent and objectName using the class specified by className. You can use this function to create any of the widgets returned by the availableWidgets() function.

The function is also used internally by the Loader class whenever it has to create a widget. For that reason, you can subclass the Loader class and reimplement this function to intervene the process of constructing an user interface or widget.

See also availableWidgets() and load().

### QWidget * Loader::load ( QIODevice * device, QWidget * parent = 0 )

Loads a form from the given device and creates a new widget with the given parent to hold its contents.

See also createWidget().

### QStringList Loader::pluginPaths () const

Returns a list naming the paths the loader searches when locating custom widget plugins.

See also addPluginPath() and clearPluginPaths().