SignalTransition QML Type

The SignalTransition type provides a transition based on a Qt signal. More...

Import Statement: import QtQml.StateMachine 1.0
Since: Qt 5.4
Inherits:

QSignalTransition

Properties

Detailed Description

SignalTransition is part of The Declarative State Machine Framework.

Example Usage


  import QtQuick 2.0
  import QtQml.StateMachine 1.0 as DSM

  Rectangle {
      DSM.StateMachine {
          id: stateMachine
          initialState: state
          running: true
          DSM.State {
              id: state
              DSM.SignalTransition {
                  targetState: finalState
                  signal: button.clicked
                  guard: guardButton.checked
              }
          }
          DSM.FinalState {
              id: finalState
          }
          onFinished: Qt.quit()
      }
      Row {
          spacing: 2
          Button {
              id: button
              text: "Finish state"
          }

          Button {
              id: guardButton
              checkable: true
              text: checked ? "Press to block the SignalTransition" : "Press to unblock the SignalTransition"
          }
      }
  }


See also StateMachine, FinalState, and TimeoutTransition.

Property Documentation

guard : bool

Guard conditions affect the behavior of a state machine by enabling transitions only when they evaluate to true and disabling them when they evaluate to false.

When the signal associated with this signal transition is emitted the guard condition is evaluated. In the guard condition the arguments of the signal can be used as demonstrated in the example below.


  import QtQuick 2.0
  import QtQml.StateMachine 1.0 as DSM

  Rectangle {
      Button {
          anchors.fill: parent
          id: button
          DSM.StateMachine {
              DSM.State {
                  DSM.SignalTransition {
                      targetState: finalState
                      signal: button.mysignal
                      // the guard condition uses the mystr string argument from mysignal
                      guard: mystr == "test"
                  }
              }
              DSM.FinalState {
                  id: finalState
              }
          }
          // define the signal the SignalTransition is connected with
          signal mysignal(string mystr)
          // on clicking the button emit the signal with a single string argument
          onClicked: button.mysignal("test")
      }
  }

See also signal.


signal : signal

The signal which is associated with this signal transition.


  import QtQuick 2.0
  import QtQml.StateMachine 1.0 as DSM

  Rectangle {
      Button {
          anchors.fill: parent
          id: button
          DSM.StateMachine {
              DSM.State {
                  DSM.SignalTransition {
                      targetState: finalState
                      signal: button.clicked
                  }
              }
              DSM.FinalState {
                  id: finalState
              }
          }
      }
  }