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StateMachine<TState>

Purpose: Core state machine with state and transition caching. Manages the state lifecycle (OnEnter → OnUpdate → OnExit), automatic transition evaluation, and provides observation events. TState must implement IState.

API

Method / Property Description
StateMachine(bool enableStateCaching = true, bool enableTransitionCaching = true) Constructor. Caching speeds up repeated state/transition usage.
TState CurrentState { get; } Currently active state.
TState PreviousState { get; } Previous state (before the last transition).
void ChangeState<T>() Switch state by type. Calls OnExit on old, OnEnter on new.
void ChangeState(TState newState) Switch state by instance.
bool TryChangeState<T>() Try to switch state. Returns true if transition conditions allow it.
bool CanTransitionTo<T>() Check if transition to the given type is allowed (without executing).
T GetOrCreateState<T>() Get state from cache or create a new one.
void RegisterTransition(StateTransition) Register a transition rule.
void UnregisterTransition(StateTransition) Remove a transition rule.
IReadOnlyList<StateTransition> GetAvailableTransitions(Type) All available transitions from the given state type.
void EvaluateTransitions() Evaluate all transitions and execute the first matching one.
void Update() Call OnUpdate() on the current state. Call from MonoBehaviour.Update().
void FixedUpdate() Call OnFixedUpdate() on the current state.
void LateUpdate() Call OnLateUpdate() on the current state.
void Stop() Exit the current state without entering another (sets CurrentState to null).
void ClearStateCache() Clear the state instance cache.
void ClearTransitionCache() Clear the transition cache.

Events

Event Parameters Description
OnStateChanged (TState previous, TState current) State changed (after exit/enter).
OnStateEntered (TState entered) Entered a new state.
OnStateExited (TState exited) Exited a state.
OnTransitionEvaluated (StateTransition, bool passed) Result of a transition evaluation.

Examples

No-Code (Inspector)

For No-Code usage, use StateMachineBehaviour — a MonoBehaviour wrapper. Configure states and transitions in Inspector, wire actions via StateAction.

Code

public class EnemyAI : MonoBehaviour
{
    private StateMachine<IState> sm;

    void Awake()
    {
        sm = new StateMachine<IState>();

        // Register transition Idle → Chase when player detected
        sm.RegisterTransition(new StateTransition
        {
            FromStateType = typeof(IdleState),
            ToStateType = typeof(ChaseState)
        });

        sm.ChangeState<IdleState>();
    }

    void Update()
    {
        sm.Update();
        sm.EvaluateTransitions();
    }
}

See Also