Class StateMachine<StateT, EventT>

State machine class.

This class manages state machines and their events emits.

Emitted events

The state machines emit 4 event types:

• onEnterState(enteredState: StateT) - Emitted when the state machine enters a new state. If the entered state has subStates, the event will be emitted for each subStateMachine, from top to the bottom.
• onLeaveState(leftState: StateT) - Emitted when the state machine leaves a state. If the left state has subStates, the event will be emitted for each subStateMachine, from the bottom to the top.
• onStateChange(srcState: StateT, dstState: StateT, event: EventT) - Emitted when a transition happens. The source state and the destination state represent the deepest states of the transition.
• srcStates: StateT[], dstStates: StateT[], event: EventT) - Emitted when a transition happens. The source states and the destination states contain all the subStates of the source and destination states, from top to the bottom.

History

The history configuration gives the possibility to specify if leaving a state will reset the sub state machine to the initial state or not. If the history flag is set to true, the sub state machine is not reset and when the parent state machine enters the state back, the old state of the sub state machine is restored. The history configuration can be optionally set through the setInitialState call. Default value is 'false'.

Transition between current SM state and subSM states

Transitions between current state machine and states of the subStateMachines can be defined, only if the source state or the destination state represent states of the state machine for which the transition is defined.

// Example (see StateMachine uml from Usage):
stateMachine.addTransition('eventName', 'NotInitialized', 'Initialized') //  -> OK, both states are state of stateMachine
stateMachine.addTransition('eventName', 'NotListening', 'Listening') // -> throws, none of the states is a state of stateMachine
stateMachine.addTransition('eventName', 'NotInitialized', 'Listening') // -> OK, 'NotInitialized' is a state of stateMachine and 'Listening' is a sub state
stateMachine.addTransition('eventName', 'NotListening', 'NotInitialized') // -> OK, 'NotInitialized' is a state of stateMachine and 'NotListening' is a sub state
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Usage:

The following state machine will be created in typescript: hide empty description [] -> NotInitialized Initialized -left-> NotInitialized : shutdown NotInitialized -right-> Initialized[H] : init state Initialized { [] --> NotListening NotListening -right-> Listening : startListen Listening -left-> NotListening : stopListen }

// The state machine must be created from bottom to the top. Therefore the sub state machine is created first.
const subStateMachine = new StateMachine<SMStates, SMEvents>();
subStateMachine.addState('Listening');
subStateMachine.addState('NotListening');
// history configuration is set through 'setInitialState'
subStateMachine.setInitialState('NotListening',true);
subStateMachine.addTransition('startListen','NotListening','Listening');
subStateMachine.addTransition('stopListen', 'Listening', 'NotListening');

// Create top state machine and set the subState machine with addState.
const stateMachine = new StateMachine<SMStates, SMEvents>();
stateMachine.addState('NotInitialized');
// set the subStateMachine for the 'Initialized' state
stateMachine.addState('Initialized', subStateMachine);
stateMachine.setInitialState('shutdown');
stateMachine.addTransition('init','NotInitialized','Initialized');
stateMachine.addTransition('shutdown', 'Initialized', 'NotInitialized');

// listen for events
stateMachine.onEnterState( enteredState => {
    //...
}

// trigger events
stateMachine.triggerEvent('init');
stateMachine.triggerEvent('startListen');
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