Qt 5.7 | Qt Quick | QML Types | PropertyChanges QML Type

Qt 5.7.1 Reference Documentation

# PropertyChanges QML Type

Describes new property bindings or values for a state. More...

Import Statement: | import QtQuick 2.7

- 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 2.0

      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 ParentChange instead.

### Resetting property values

The `undefined` value can be used to reset the property value for a state. In the following example, when `myText` 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 type can be used to force an immediate property change.

See the PropertyAction documentation for more details.

Note: The visible and enabled properties of Item do not behave exactly the same as other properties in PropertyChanges. Since these properties can be changed implicitly through their parent's state, they should be set explicitly in all PropertyChanges. An item will still not be enabled/visible if one of its parents is not enabled or visible.

See also States example, Qt Quick States, and Qt QML.

## Property Documentation

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.