C#数据结构-有限状态机

有限状态机FSM的要点是：

拥有一组状态，并且可以在这组状态之间进行切换。
状态机同时只能在一个状态。
一连串的输入或事件被发送给机器。
每个状态都有一系列的转换，转换与输入和另一状态相关。当输入进来，如果它与当前状态的某个转换匹配，机器转为转换所指的状态。
目前而言，游戏编程中状态机的实现方式，有两种可以选择：

用枚举配合switch case语句。
实现多态（也就是状态模式）。
状态模式的经典定义：允许对象在当内部状态改变时改变其行为，就好像此对象改变了自己的类一样

状态模式的实现要点，主要有三点：

为状态定义一个接口。
为每个状态定义一个类。
恰当地进行状态委托。
注：下面的代码在unity中用C#实现，不过只是借用了unity的输入操作，对于理解有限状态机，没有阻碍。

初始化是站立状态；
按下向上的方向键，可以跳跃；在跳跃的状态，按向下的方向键，可以下斩，按向上的方向键，不做处理；
按下向下的方向键，可以下蹲；在下蹲的状态，按向下的方向键，不做处理，按向上的方向键，恢复站立状态；
代码来自于这里超链接

状态接口实现：

public interface HeroineBaseState
{
void HandleInput();
}
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站立状态实现：

using UnityEngine;

public class StandingState : HeroineBaseState
{
private Heroine _heroine;
public StandingState(Heroine heroine)
{
_heroine = heroine;
Debug.Log(“进入站立状态！”);
}

public void HandleInput()
{
if (Input.GetKeyDown(KeyCode.UpArrow))
{
Debug.Log(“get KeyCode.UpArrow!”);
_heroine.SetHeroineState(new JumpingState(_heroine));
}
if (Input.GetKeyDown(KeyCode.DownArrow))
{
Debug.Log(“get KeyCode.DownArrow!”);
_heroine.SetHeroineState(new DuckingState(_heroine));
}
}
}

跳跃状态实现：

using UnityEngine;

public class JumpingState : HeroineBaseState
{

private Heroine _heroine;
public JumpingState(Heroine heroine)
{
_heroine = heroine;
Debug.Log(“进入跳跃状态！”);
}

public void HandleInput()
{
if (Input.GetKeyDown(KeyCode.UpArrow))
{
Debug.Log(“已经在跳跃状态中！”);
return;
}
if (Input.GetKeyDown(KeyCode.DownArrow))
{
Debug.Log(“get KeyCode.DownArrow!”);
_heroine.SetHeroineState(new DrivingState(_heroine));
}
}
}

下蹲状态实现：

using UnityEngine;

public class DuckingState : HeroineBaseState
{
private Heroine _heroine;
public DuckingState(Heroine heroine)
{
_heroine = heroine;
Debug.Log(“进入下蹲躲避状态！”);
}

public void HandleInput()
{
if (Input.GetKeyDown(KeyCode.DownArrow))
{
Debug.Log(“已经在下蹲躲避状态中！”);
return;
}
if (Input.GetKeyUp(KeyCode.UpArrow))
{
Debug.Log(“get GetKeyUp.UpArrow!”);
_heroine.SetHeroineState(new StandingState(_heroine));
}
}
}

下斩状态实现：

using UnityEngine;

public class DrivingState : HeroineBaseState
{
private Heroine _heroine;
public DrivingState(Heroine heroine)
{
_heroine = heroine;
Debug.Log(“进入下斩状态！”);
}

public void HandleInput()
{
if (Input.GetKeyDown(KeyCode.UpArrow))
{
Debug.Log(“get KeyCode.UpArrow!”);
_heroine.SetHeroineState(new StandingState(_heroine));
}
}
}

女主角实现：

public class Heroine
{
HeroineBaseState _state;

public Heroine()
{
_state = new StandingState(this);
}

public void SetHeroineState(HeroineBaseState newState)
{
_state = newState;
}

public void Update()
{
_state.HandleInput();
}

}

测试代码，在Unity里要挂在一个GameObject上执行。

using UnityEngine;

public class TestHeroine : MonoBehaviour
{
private Heroine _heroine;

// 初始化调用，先执行
void Start()
{
_heroine = new Heroine();
}

// 每帧调用一次
void Update()
{
_heroine.Update();
}
}

上面用的接口，还可以用虚函数或者抽象函数来实现多态。下面模拟了银行存款取款，账户的状态的变化。

C#代码实现：

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using System;

namespace StructScript
{

public class StateScript
{
static void Main(string[] args)
{
Account account = new Account();
account.Add(500);
account.Add(3000);
account.Remove(1000);
account.Remove(10000);

Console.ReadLine();
}
}

public class Account
{
private State state;

public Account()
{
state = new RedState(0.0, this);
}

public State State
{
get { return state; }
set { state = value; }
}

public void Add(int amount)
{
Console.WriteLine(“Add ” + amount);
state.Add(amount);
Console.WriteLine(“Balance: ” + state.Balance);
Console.WriteLine(“State: ” + state.GetType().Name);
}

public void Remove(int amount)
{
Console.WriteLine(“Remove ” + amount);
state.Remove(amount);
Console.WriteLine(“Balance: ” + state.Balance);
Console.WriteLine(“State: ” + state.GetType().Name);
}
}

/// <summary>
/// 状态基类
/// </summary>
public abstract class State
{
protected Account account;
protected double balance;
protected double lowerLimit;
protected double upperLimit;

public Account Account
{
get { return account; }
set { account = value; }
}

public double Balance
{
get { return balance; }
set { balance = value; }
}

public abstract void Add(int amount);
public abstract void Remove(int amount);
}

/// <summary>
/// 红色账户状态
/// </summary>
public class RedState : State
{
public RedState(State state) : this(state.Balance, state.Account) { }

public RedState(double balance, Account account)
{
this.balance = balance;
this.account = account;
lowerLimit = -100.0;
upperLimit = 0.0;
}

public override void Add(int amount)
{
balance += amount;
StateChangeCheck();
}

public override void Remove(int amount)
{
Console.WriteLine(“余额不足”);
}

private void StateChangeCheck()
{
if (balance > upperLimit)
{
account.State = new SilverState(this);
}
}
}

/// <summary>
/// 银色账户状态
/// </summary>
public class SilverState : State
{
public SilverState(State state) : this(state.Balance, state.Account) { }

public SilverState(double balance, Account account)
{
this.balance = balance;
this.account = account;
lowerLimit = 0.0;
upperLimit = 1000.0;
}

public override void Add(int amount)
{
balance += amount;
StateChangeCheck();
}

public override void Remove(int amount)
{
double remain = balance – amount;
if (remain < -100)
{
Console.WriteLine(“余额不足”);
}
else
{
balance = remain;
StateChangeCheck();
}
}

private void StateChangeCheck()
{
if (balance < lowerLimit)
{
account.State = new RedState(this);
}
else if (balance > upperLimit)
{
account.State = new GoldState(this);
}
}
}

/// <summary>
/// 金色账户状态
/// </summary>
public class GoldState : State
{
public GoldState(State state) : this(state.Balance, state.Account) { }

public GoldState(double balance, Account account)
{
this.balance = balance;
this.account = account;
lowerLimit = 1000.0;
upperLimit = 10000000.0;
}

public override void Add(int amount)
{
balance += amount;
StateChangeCheck();
}

public override void Remove(int amount)
{
double remain = balance – amount;
if (remain < -100)
{
Console.WriteLine(“余额不足”);
}
else
{
balance = remain;
StateChangeCheck();
}
}

private void StateChangeCheck()
{
if (balance < 0.0)
{
account.State = new RedState(this);
}
else if (balance < lowerLimit)
{
account.State = new SilverState(this);
}
}
}
}

有限状态机