Implementing a state machine in Unity

Wikipedia : A finite state machine (English: finite-state machine, abbreviation: FSM), also known as a finite state automaton, or a state machine for short, is a mathematical model that represents a finite number of states and behaviors such as transitions and actions between these states.

This article refers to the StateMachine in quick-cocos to implement the Unity version of the finite state machine.

---

Implementation ideas:

1. Create a state machine object

public class StateMachine : MonoBehaviour {
    ...
}

1. Initialize state machine information, including events and callback functions.

// 事件
public class SMEvent
{
    readonly string name;
    readonly List<string> froms;
    readonly string to;

    public string Name { get { return name; } }
    public List<string> Froms { get { return froms; } }
    public string To { get { return to; } }

    public SMEvent(string _name, List<string> _froms, string _to)
    {
        name = _name;
        froms = _froms;
        to = _to;
    }
}

// 回调函数
Dictionary<string, Func<SMEvent, bool>> _callbacks;

1. Switching states is achieved by executing events.

public int DoEvent(string name){ ... }

1. Conditional judgment of the execution event

public bool IsReady(){...} ：返回状态机是否就绪
public string GetState(){...} ：返回当前状态
public bool IsState(string state){...} ：判断当前状态是否是参数state状态
public bool CanDoEvent(string eventName){...}：当前状态如果能完成eventName对应的event的状态转换，则返回true
public bool CanNotDoEvent(string eventName){...} ：当前状态如果不能完成eventName对应的event的状态转换，则返回true
public bool IsFinishedState(){...}：当前状态如果是最终状态，则返回true

1. execute callback function

// 在事件EVENT开始前被激活
private bool BeforeThisEvent(SMEvent smEvent) {...}


// 在离开旧状态STATE时被激活
private bool LeaveThisEvent(SMEvent smEvent) {...}


// 在进入新状态STATE时被激活
private bool EnterThisEvent(SMEvent smEvent) {...}


// 在事件EVENT结束后被激活
private bool AfterThisEvent(SMEvent smEvent) {...}


// 在任何事件开始前被激活
private bool BeforeAnyEvent(SMEvent smEvent) {...}

// 在任何事件结束后被激活
private bool AfterAnyEvent(SMEvent smEvent) {...}

// 在进入任何状态时被激活
private bool EnterAnyState(SMEvent smEvent) {...}


// 在离开任何状态时被激活
private bool LeaveAnyState(SMEvent smEvent) {...}

// 当状态发生改变的时候被激活
private bool ChangeAnyState(SMEvent smEvent) {...}

Example of use:

// 创建一个状态机实例
StateMachine fsm = gameObject.AddComponent<StateMachine>();

// 添加事件和状态
List<SMEvent> events = new List<SMEvent>();
events.Add(new SMEvent("move", new List<string> { "idle", "jump"}, "walk"));
events.Add(new SMEvent("attack", new List<string> { "idle", "walk" }, "jump"));
events.Add(new SMEvent("normal", new List<string> { "walk", "jump"}, "idle"));
events.Add(new SMEvent("lie", new List<string> { "move", "idle"}, "falldown"));

// 添加回调函数
Func<SMEvent, bool> onenteridle = x => Walk(x);
Func<SMEvent, bool> onenterwalk = x => Jump(x);
Func<SMEvent, bool> onenterjump = x => Idle(x);
Func<SMEvent, bool> onenterlie = x => FallDown(x);

Dictionary<string, Func<SMEvent, bool>> callbacks = new Dictionary<string, Func<SMEvent, bool>>();
callbacks.Add("onenternormal", onenteridle);
callbacks.Add("onentermove", onenterwalk);
callbacks.Add("onenterattack", onenterjump);
callbacks.Add("onenterlie", onenterlie);

// 初始化状态机
string initial = "idle";
fsm.SetupState(events, callbacks, initial, "", false);;

// 回调
private bool Walk(SMEvent smEvent) {
    Debug.LogError("Walk");
    return true;
}

private bool Jump(SMEvent smEvent)
{
    Debug.LogError("Jump");
    return true;
}

private bool Idle(SMEvent smEvent)
{
    Debug.LogError("Idle");
    return true;
}

private bool FallDown(SMEvent smEvent)
{
    Debug.LogError("FallDown");
    return true;
}

Instance address:

https://github.com/MagicDavid20/UnityFSM/tree/master/fsm

other:

1. State and event names can be implemented through configuration tables or enumerations
2. The specific implementation of Walk, Jump, etc. can be realized through the state mode, moving the pointer address.

---

If there are any mistakes, please point them out.

email：dxmdxm1992#gmail.com

blog: http://blog.csdn.net/david_dai_1108