Unityで使う簡単なステートマシン的な実装

StateMachine.cs

using UnityEngine;

using System.Linq;
using System.Collections;
using System.Collections.Generic;

public class StateMachine
{
	public abstract class BaseState
	{
		public virtual void OnRegister (MonoBehaviour behaviour) { }
		public virtual void OnStateEnter (MonoBehaviour behaviour) { }
		public virtual void OnStateExit (MonoBehaviour behaviour) { }
		public virtual bool OnStateUpdate (MonoBehaviour behaviour) { return true; }
	}

	public delegate string StateExitHandler (string exitStateName, BaseState exitState);
	
	private Dictionary<string, BaseState> stateMap = new Dictionary<string, BaseState> ();
	private MonoBehaviour behaviour;

	public string CurrentStateName { get; private set; }
	public BaseState CurrentState { get; private set; }

	public StateExitHandler OnStateExit;

	public StateMachine (MonoBehaviour behaviour)
	{
		this.behaviour = behaviour;
	}

	public bool RegisterState (string stateName, BaseState state)
	{
		if (string.IsNullOrEmpty (stateName) || stateMap.ContainsKey (stateName) || state == null)
		{
			return false;
		}

		stateMap [stateName] = state;

		state.OnRegister (behaviour);

		return true;
	}

	public bool Start (string firstStateName)
	{
		if (!stateMap.ContainsKey (firstStateName))
		{
			return false;
		}

		EnterState (firstStateName);

		return true;
	}

	public void Update ()
	{
		if (CurrentState == null) { return; }

		bool exit = CurrentState.OnStateUpdate (behaviour);

		if (exit)
		{
			string nextStateName = ExitState ();

			EnterState (nextStateName);
		}
	}

	private void EnterState (string stateName)
	{
		if (!string.IsNullOrEmpty(stateName) && stateMap.ContainsKey (stateName))
		{
			CurrentStateName = stateName;
			CurrentState = stateMap [stateName];
			CurrentState.OnStateEnter (behaviour);
		}
	}

	private string ExitState ()
	{
		string nextStateName = null;
		
		if (CurrentState != null)
		{
			CurrentState.OnStateExit (behaviour);

			nextStateName = OnStateExit (CurrentStateName, CurrentState);

			CurrentState = null;
			CurrentStateName = null;
		}

		return nextStateName;
	}
}