SignalTransition QML Type

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

Import Statement: import QtQml.StateMachine 1.15
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(mystr: string)
         // 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
             }
         }
     }
 }