DeclarativeStateTreeBuilder class

Provides methods to describe a state tree.

States are defined and added to the state tree are described by calling methods such state, dataState, and finalState. A state tree or state machine can be nested within another state tree with the machineState method.

enum Messages { toggle }
var offState = StateKey('off');
var onState = StateKey('on');

DeclarativeStateTreeBuilder switchBuilder() {
  // A simple switch with on and off states
  var treeBuilder = DeclarativeStateTreeBuilder(initialChild: offState)
  treeBuilder.state(offState, (b) {
    b.onMessageValue(Messages.toggle, (b) => b.goTo(onState));
  })
  treeBuilder.state(onState, (b) {
    b.onMessageValue(Messages.toggle, (b) => b.goTo(offState));
  });
  return treeBuilder;
}

Once a DeclarativeStateTreeBuilder has been initialized with the desired states, it can be used to create a state machine. The state machine will create and manage its own instance of the state tree defined by the builder.

 var declBuilder = switchBuilder();
 var stateMachine = TreeStateMachine(StateTreeBuilder(declBuilder));

Note that a single state tree builder instance can be used to create multiple state machine instances.

A textual description of the state tree can be produced by calling format method, passing a StateTreeFormatter (for example a DotFormatter) representing the desired output format.