Qt Reference Documentation

# QML PropertyChanges Element

The PropertyChanges element describes new property bindings or values for a state. More...

This element was introduced in Qt 4.7.

- List of all members, including inherited members

## Properties

- explicit : bool
- restoreEntryValues : bool
- target : Object

## Detailed Description

PropertyChanges is used to define the property values or bindings in a State. This enables an item's property values to be changed when it changes between states.

To create a PropertyChanges object, specify the target item whose properties are to be modified, and define the new property values or bindings. For example:

     import QtQuick 1.0

     Item {
         id: container
         width: 300; height: 300

         Rectangle {
             id: rect
             width: 100; height: 100
             color: "red"

             MouseArea {
                id: mouseArea
                anchors.fill: parent
             }

             states: State {
                name: "resized"; when: mouseArea.pressed
                PropertyChanges { target: rect; color: "blue"; height: container.height }
             }
         }
     }

When the mouse is pressed, the Rectangle changes to the resized state. In this state, the PropertyChanges object sets the rectangle's color to blue and the `height` value to that of `container.height`.

Note this automatically binds `rect.height` to `container.height` in the resized state. If a property binding should not be established, and the height should just be set to the value of `container.height` at the time of the state change, set the explicit property to `true`.

A PropertyChanges object can also override the default signal handler for an object to implement a signal handler specific to the new state:

     PropertyChanges {
         target: myMouseArea
         onClicked: doSomethingDifferent()
     }

Note: PropertyChanges can be used to change anchor margins, but not other anchor values; use AnchorChanges for this instead. Similarly, to change an Item's parent value, use ParentChanges instead.

### Resetting property values

The `undefined` value can be used to reset the property value for a state. In the following example, when `theText` changes to the widerText state, its `width` property is reset, giving the text its natural width and displaying the whole string on a single line.

     Rectangle {
         width: 300; height: 200

         Text {
             id: myText
             width: 50
             wrapMode: Text.WordWrap
             text: "a text string that is longer than 50 pixels"

             states: State {
                 name: "widerText"
                 PropertyChanges { target: myText; width: undefined }
             }
         }

         MouseArea {
             anchors.fill: parent
             onClicked: myText.state = "widerText"
         }
     }

### Immediate property changes in transitions

When Transitions are used to animate state changes, they animate properties from their values in the current state to those defined in the new state (as defined by PropertyChanges objects). However, it is sometimes desirable to set a property value immediately during a Transition, without animation; in these cases, the PropertyAction element can be used to force an immediate property change.

See the PropertyAction documentation for more details.

See also states example, States, and QtDeclarative.

## Property Documentation

read-only explicit : bool

If explicit is set to true, any potential bindings will be interpreted as once-off assignments that occur when the state is entered.

In the following example, the addition of explicit prevents `myItem.width` from being bound to `parent.width`. Instead, it is assigned the value of `parent.width` at the time of the state change.

     PropertyChanges {
         target: myItem
         explicit: true
         width: parent.width
     }

By default, explicit is false.

restoreEntryValues : bool

This property holds whether the previous values should be restored when leaving the state.

The default value is `true`. Setting this value to `false` creates a temporary state that has permanent effects on property values.

target : Object

This property holds the object which contains the properties to be changed.