Unity--FSM有限状态机

有限状态机，先理解是干什么的，有限表示这个是有限度的不是无限的，状态，指的是所拥有的所有状态，这么来理解，人有情绪，比如说生气，无感，喜悦，难过，生气，幸福等，那么这些情绪是固有的几种，是所谓有限，那么那些情绪就是不同的状态，人可以在这些状态之中进行转换，此时是开心的，下一秒有可能就是生气的，这就是有限状态机的原理。

这一篇代码稍微多了一点，咱们一点一点来说：

---

using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public enum Transition
{
    NullTransition = 0, 
    NoSeePlayer,
    SeePlayer,
    GamePause
}

public enum StateID
{
    NullStateID = 0, 
    IdleState,
    PatrolState,
    ChaseState
}

public abstract class FSMState
{
    protected FSMSystem fsm;

    protected Dictionary<Transition, StateID> map = new Dictionary<Transition, StateID>();
    protected StateID stateID;
    public StateID ID { get { return stateID; } }
    
    public FSMState(FSMSystem fsm)
    {
        this.fsm = fsm;
    }

    public void AddTransition(Transition trans, StateID id)
    {
        if (trans == Transition.NullTransition)
        {
            Debug.LogError("FSMState ERROR: NullTransition is not allowed for a real transition");
            return;
        }

        if (id == StateID.NullStateID)
        {
            Debug.LogError("FSMState ERROR: NullStateID is not allowed for a real ID");
            return;
        }
        if (map.ContainsKey(trans))
        {
            Debug.LogError("FSMState ERROR: State " + stateID.ToString() + " already has transition " + trans.ToString() +
                           "Impossible to assign to another state");
            return;
        }

        map.Add(trans, id);
    }
    
    public void DeleteTransition(Transition trans)
    {
        if (trans == Transition.NullTransition)
        {
            Debug.LogError("FSMState ERROR: NullTransition is not allowed");
            return;
        }
        
        if (map.ContainsKey(trans))
        {
            map.Remove(trans);
            return;
        }
        Debug.LogError("FSMState ERROR: Transition " + trans.ToString() + " passed to " + stateID.ToString() +
                       " was not on the state's transition list");
    }
    
    public StateID GetOutputState(Transition trans)
    {
        if (map.ContainsKey(trans))
        {
            return map[trans];
        }