如何使类类型安全

Question

using System;
using System.Reflection;
using UnityEngine;
public class StateMachine<TStates> where TStates : Enum
{
private TStates initialState;
private TStates currentState;
private MonoBehaviour component;
public StateMachine(MonoBehaviour component)
{
this.component = component;
}
public StateMachine(MonoBehaviour component, TStates initialState)
{
this.component = component;
this.initialState = initialState;
SetState(this.initialState);
}

public void SetState(TStates newState)
{
Type componentType = component.GetType();

if (currentState != null)
{
if (currentState.Equals(newState))
return;

componentType.GetMethod("On" + currentState + "Exit", BindingFlags.NonPublic | BindingFlags.Instance)?.Invoke(component, null);
}
else
initialState = newState;
currentState = newState;
componentType.GetMethod("On" + currentState + "Enter", BindingFlags.NonPublic | BindingFlags.Instance).Invoke(component, null);
}
public void Update()
{
Type componentType = component.GetType();
if (currentState != null)
componentType.GetMethod("On" + currentState + "Update", BindingFlags.NonPublic | BindingFlags.Instance)?.Invoke(component, null);
}
public void Reset()
{
if (initialState != null)
SetState(initialState);
}
}

我有一个有限状态机，我试着自己做，它工作得很好。然而，人们告诉我，这不是打字安全。

他们告诉我使用switch语句，但我不知道如何实现它们。

有什么办法可以让它打字安全吗？

Answer 1

public interface IStateHandle<TStates> where TStates : Enum
{
void OnEnter(TStates state);
void OnUpdate(TStates state);
void OnExit(TStates state);
}
public class StateMachine<TStates> where TStates : Enum
{
IStateHandle<TStates> _handle;
TStates _currentState;
public StateMachine(IStateHandle<TStates> handle)
{
_handle = handle;
}
public void Update()
{
_handle.OnUpdate(_currentState);
}
}

Answer 2

例如，您可以将您的状态替换为只使用方法的状态类型，例如：

public interface IState{
void Exit();
void Enter();
void Update();
}

并为您想要的每个状态提供一个实现。您还可以有一个实现，将每个方法的实现委托给一个委托。

Answer 3

通过引入公共基类或接口，您可以轻松地使状态机类型安全，您的状态应该从中继承。鉴于此，实现状态机设计模式非常简单：

public interface IState
{
void Handle(Context context);
}
public class Walk : IState
{
public void Handle(Context context)
{
context.State = new Shoot();
}
}
public class Shoot : IState
{
public void Handle(Context context)
{
context.State = new Walk();
}
}
public class Context
{
public Context(IState state)
{
this.State = state;
}
public IState State { get; set; }
public void Request()
{
this.State.Handle(this);
}
}