qt-creator/doc/src/qtquick/qtquick-connection-editor.qdoc

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/*!
    \contentspage {Qt Creator Manual}
    \previouspage qmldesigner-pathview-editor.html
    \page qmldesigner-connections.html
    \nextpage quick-components.html

    \title Adding Connections

    You can use the \uicontrol {Connections} view to:

    \list

        \li Connect objects to signals.

        \li Specify dynamic properties for objects.

        \li Create bindings between the properties of two objects.

        \li Manage backend QObjects.

    \endlist

    For examples of adding connections, see
    \l{Creating Scalable Buttons and Borders}.

    \section1 Connecting Objects to Signals

    To connect objects to signals in QML, create \l{Connections} objects.

    \image qmldesigner-connections.png

    To create the connections:

    \list 1

        \li Select the \uicontrol {Connections} tab.

        \li Select the \inlineimage plus.png
            (\uicontrol Add) button to add a connection.

        \li Select \uicontrol Target to add the object to connect to a signal.

        \li Select \uicontrol {Signal Handler} to select the signal that the connection
            will listen to from a list of all signals available for the object.

        \li Select \uicontrol Actions to specify the action to perform when
            the signal is emitted. You use JavaScript to specify the actions.

    \endlist

    \section1 Specifying Dynamic Properties

    You can bind \l{Properties} to dynamic expressions to define global properties for an
    object that can be read by other objects. For example, you can specify
    global properties for the root object that you can use in the child objects.

    \image qmldesigner-dynamicprops.png

    To specify dynamic properties for an object:

    \list 1

        \li Select the \uicontrol {Properties} tab.

        \li Select \uicontrol Item to select the object to specify the property for.

        \li Select \uicontrol Property to give a name to the property.

        \li Select \uicontrol {Property Type} to specify the type of the property.

        \li Select \uicontrol {Property Value} to specify the value of the property.

    \endlist

    \section1 Adding Bindings Between Properties

    To dynamically change the behavior of an object, you can create a
    \l{Property Binding} between the properties of two objects.

    \image qmldesigner-bindings.png

    To bind a property of an object to the property of another object:

    \list 1

        \li Select the \uicontrol {Bindings} tab.

        \li Select the \inlineimage plus.png
            (\uicontrol Add) button to add a binding.

        \li Select \uicontrol Item to select the target object whose property you want
            to change dynamically.

        \li Select \uicontrol Property to select the property to bind to a source
            property.

        \li Select \uicontrol {Source Item} to select the object whose property you
            want to use to determine the behavior of the target object.

        \li Select \uicontrol {Source Property} to select the property to bind the
            target property to.

    \endlist

    \section1 Managing C++ Backend Objects

    Many applications provide QObject objects implemented in C++ that work as a
    bridge between QML and C++. Such objects are typically registered with
    qmlRegisterType or qmlRegisterSingletonType and then used by QML to
    communicate with the C++ backend. Another example of such objects are the
    state machines created by the \l {Using the Qt SCXML Compiler (qscxmlc)}
    {Qt SCXML Compiler}.

    Backend objects in a QML file are accessible if the QML file contains the
    required imports. In addition, for a non-singleton QObject, a dynamic
    property that contains the QObject must be specified.

    A \e local QObject is instantiated in the current \e .qml file, as follows:

    \badcode
    property MyType myType: MyType {}.
    \endcode

    Otherwise the property is just defined, as follows:

    \badcode
    property MyType myType
    \endcode

    To manage backend objects:

    \list 1

        \li Select the \uicontrol Backends tab to view accessible backend
            objects.

            \image qmldesigner-backends.png

        \li Select the \inlineimage plus.png
            (\uicontrol Add) button to add a backend object in the
            \uicontrol {Add New C++ Backend} dialog.

        \li In the \uicontrol Type field, select the type of the backend QObject
            to add.

        \li Select the \uicontrol {Define object locally} check box if the
            QObject is not registered as a singleton.

        \li Select \uicontrol OK to add the required import and to create the
            property for a non-singleton object.

    \endlist

*/