SCXML Calculator

Calculator uses Qt SCXML to implement the Calculator Example presented in the SCXML Specification.

The state machine is specified in the statemachine.scxml file and compiled into the CalculatorStateMachine class. The user interface is created using Qt Quick.

Running the Example

You can run the example from:

• Qt Creator

  Open the Welcome mode and select the example from Examples. For more information, see Qt Creator: Tutorial: Build and run.

• Qt Extension for Visual Studio Code

  Run the Qt: Open Qt examples command from the Command Palette, and select the example from the list. For more information, see Qt Extension for Visual Studio Code: Tutorial: Build and run.

Instantiating the State Machine

We make the generated CalculatorStateMachine class available to QML by declaring it as a QML type in the calculator-qml.h file:

 struct CalculatorStateMachineRegistration
 {
     Q_GADGET
     QML_FOREIGN(CalculatorStateMachine)
     QML_NAMED_ELEMENT(CalculatorStateMachine)
     QML_ADDED_IN_VERSION(1, 0)
 };

We instantiate a CalculatorStateMachine and listen to the updateDisplay event. When it occurs, we change the text on the calculator display:

     CalculatorStateMachine {
         id: statemachine
         running: true
         EventConnection {
             events: ["updateDisplay"]
             onOccurred: (event)=> resultText.text = event.data.display
         }
     }

When users press the calculator buttons, the buttons submit events to the state machine:

         Button {
             id: resultButton
             x: 3 * width
             y: parent.height / 5
             textHeight: y - 2
             fontHeight: 0.4
             width: parent.width / 4
             height: y * 4
             color: pressed ? "#e0b91c" : "#face20"
             text: "="
             onClicked: statemachine.submitEvent("EQUALS")
         }

Example project @ code.qt.io