- Qt 6.4
- Qt SCXML
- Qt SCXML Examples
- Qt SCXML Invoke Example (Dynamic)
- Qt 6.4.3 Reference Documentation

# Qt SCXML Invoke Example (Dynamic)

Invokes a dynamically loaded nested state machine.

Invoke Example (Dynamic) demonstrates how to use the `<invoke>` element with generated nested state-machines, where the SCXML file is dynamically loaded. The `<invoke>` element is used to create an instance of an external service.

#### Running the Example

To run the example from Qt Creator, open the Welcome mode and select the example from Examples. For more information, visit Building and Running an Example.

#### 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:

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

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

#### Dynamically Loading the State Machine

We link against the Qt SCXML module by adding the following line to the project build files.

With qmake to the invoke-dynamic.pro

     QT += qml scxml

With cmake to the CMakeLists.txt

     find_package(Qt6 REQUIRED COMPONENTS Core Gui Qml Scxml)

     target_link_libraries(invoke-dynamic PUBLIC
         Qt6::Core
         Qt6::Gui
         Qt6::Qml
         Qt6::Scxml
     )

We dynamically create the state machine, as follows:

     import QtScxml

     MainView {
         stateMachine: directions.stateMachine

         StateMachineLoader {
             id: directions
             source: "qrc:///statemachine.scxml"
         }

Example project @ code.qt.io