Qt 5.8 | Qt QML | QML Types | SignalTransition QML Type

Qt 5.8.0 Reference Documentation

# 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

- List of all members, including inherited members

## Properties

- guard : bool
- signal : signal

## 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
                  }
              }
          }
      }