TODO:

• Bump Events (if an event happens during a State, it is just added back to the queue)
• Make the state machine definition a shared asset
• Precompute route between states defines by events (no more route search at runtime)

Usage Example

Declaration

UPROPERTY(Instanced) UHierarchicalStateMachine* m_stateMachine;

Definition

m_stateMachine = CreateDefaultSubobject<UHierarchicalStateMachine>(TEXT("stateMachine"));
STATEMACHINE_DEFINITION(m_stateMachine)
(
  TRACK(RootTrack) // First level of the state machine must contain Tracks and not States. It can contain several Tracks
  (
    // Default state is just like any state, except it will be the state that 
    // is entered in the track if the transition does not define a specific destination state
    DEFAULT_STATE(State1) 
    (
      STATE_ENTER(this, &MyClass::State1_Enter);  // these are just delegates to you class methods
      STATE_TICK(this, &MyClass::State1_Tick);    // function prototype for TICK is void(float) the parameter is dt
      STATE_EXIT(this, &MyClass::State1_Exit);    // function prototype for ENTER/EXIT is void()
    );
        
    STATE(State2)
    (
      STATE_TICK(this, &MyClass::State2_Tick); //You can just declare the function you need between ENTER TICK & EXIT
          
      TRACK(SubTrack1) // Every State can have several tracks, Every Track can have several States
      (
        DEFAULT_STATE(SubState1)();
        STATE(SubState2)
        (
          // ...
        );
      );
          
      TRACK(SubTrack2)();
    );
  );
    
  // Every Track Name must be unique, every State Name must be unique as well

  TRANSITION_EVENT("EventName", SubState2, State1);
  TRANSITION_EVENT("EventName2", SubState2, SubState1); // Transition must declared from one state to another
  TRANSITION_EVENT("EventName3", Track, SubState1); // Transition can also be declared from a track to a state
);

Usage

m_stateMachine->Start();        // Starts State Machine, enters all defaults states from the highest to the deepests
m_stateMachine->Tick(DeltaTime) // Dequeue events, enter/exit states accordingly, ticks all current states, Dequeue events again and enter/exit states accordingly
m_stateMachine->Stop();         // Stops State Machine, exits all current states from the deepests to the highest

m_stateMachine->PostEvent("EventName"); // Post an event that may result in a state transition.

m_stateMachine->bImmediatelyDequeueEvents = true; // Sets the state machine to dequeue events immediately during a PostEvent calls

References

This state machine is greatly inspired and loosely adapted from Wiwila's work on State Machines.