Qt SCXML Invoke Example (Static)

Invokes a compiled nested state machine.

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The Qt Company Ltd.

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Publié le 27 décembre 2024 - Mis à jour le 27 décembre 2024

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Qt SCXML Invoke Example (Static)▲

Invoke Example (Static) demonstrates how to use the <invoke> element with generated nested state-machines, where the SCXML file is compiled to a C++ class. The <invoke> element is used to create an instance of an external service.

Running the Example▲

To run the example from http://, open the Welcome mode and select the example from Examples. For more information, visit http://.

Invoking the State Machine▲

In statemachine.scxml, we specify a state machine with the name Directions of type http://www.w3.org/TR/scxml/ to invoke:

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&lt;scxml
    xmlns="http://www.w3.org/2005/07/scxml"
    version="1.0"
    name="Directions"
    initial="anyplace"
&gt;
    &lt;state id="anyplace"&gt;
        &lt;transition event="goNowhere" target="nowhere"/&gt;
        &lt;transition event="goSomewhere" target="somewhere"/&gt;

        &lt;state id="nowhere"/&gt;
        &lt;state id="somewhere"&gt;
            &lt;invoke type="http://www.w3.org/TR/scxml/"&gt;
                &lt;content&gt;
                    &lt;scxml name="anywhere" version="1.0"&gt;
                        &lt;state id="here"&gt;
                            &lt;transition event="goThere" target="there"/&gt;
                        &lt;/state&gt;
                        &lt;state id="there"&gt;
                            &lt;transition event="goHere" target="here"/&gt;
                        &lt;/state&gt;
                    &lt;/scxml&gt;
                &lt;/content&gt;
            &lt;/invoke&gt;
        &lt;/state&gt;
    &lt;/state&gt;
&lt;/scxml&gt;

Compiling the State Machine▲

We link against the Qt SCXML module by adding the following line to the invoke-static.pro file:

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QT += qml scxml

We then specify the state machine to compile:

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STATECHARTS = ../invoke-common/statemachine.scxml

The Qt SCXML Compiler, qscxmlc, is run automatically to generate statemachine.h and statemachine.cpp, and to add them to the HEADERS and SOURCES variables for compilation.

Instantiating the State Machine▲

We instantiate the generated Directions class in the invoke-static.cpp file, as follows:

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#include "statemachine.h"

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);

    qmlRegisterType&lt;Directions&gt;("Directions", 1, 0, "Directions");

    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/invoke-static.qml")));
    if (engine.rootObjects().isEmpty())
        return -1;

    return app.exec();
}

List of Files▲

Files:

List of Files▲

invoke-static/invoke-static.cpp
invoke-static/invoke-static.pro
invoke-static/invoke-static.qml
invoke-static/invoke-static.qrc

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