Qt SCXML Calculator Example#

../_images/calculator.png

A widget-based application that implements the Calculator example presented in the SCXML Specification.

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 Widgets.

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.

Compiling the State Machine#

We link against the Qt SCXML module by adding the following lines to the example’s build files.

  • .pro*

when using qmake:#

We then specify the state machine to compile:

  • CMakeLists.txt*

when using cmake:#

We then specify the state machine to compile:

The statechart directives STATECHARTS or qt6_add_statecharts invoke the Qt SCXML Compiler, qscxmlc, which is run automatically to generate statemachine.h and statemachine.cpp, which are then added appropriately as headers and sources for compilation.

Instantiating the State Machine#

We instantiate the generated CalculatorStateMachine class in the calculator-widgets.cpp file, as follows:

Connecting to Active Properties#

After instantiating the state machine, we can connect to the active properties of the states, as follows:

The state machine can notify other code when events occur:

We connect to the updateDisplay event to display the data passed by the events:

Example project @ code.qt.io