用 State Pattern 来实现一个简单的 状态机

首先要理解 State Pattern 模式。

http://www.dofactory.com/net/state-design-pattern

Definition

Allow an object to alter its behavior when its internal state changes. The object will appear to change its class.

 

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UML class diagram

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Participants

    The classes and objects participating in this pattern are:

• Context  (Account)
  • defines the interface of interest to clients
  • maintains an instance of a ConcreteState subclass that defines the current state.
• State  (State)
  • defines an interface for encapsulating the behavior associated with a particular state of the Context.
• Concrete State  (RedState, SilverState, GoldState)
  • each subclass implements a behavior associated with a state of Context

先画个状态机用来接收和处理数据。

开始定义Base状态和各个状态

    public abstract class StateBase
    {
        public abstract void Enter(Monitor context);

        public virtual void Exit(Monitor context)
        {
            Console.WriteLine("Exiting current state: {0}", context.CurrentState.StateName); 
        }

        public string StateName
        {
            get;
            set;
        }
    }

    public class ConnectState : StateBase
    {
        public ConnectState()
        {
            this.StateName = "Connect"; 
        }
        public override void Enter(Monitor context)
        {
            Console.WriteLine("Enter - {0}", context.CurrentState.StateName);
            context.MoveToNextState(new ReceiveDataState()); 
        }
    }

Create a context class, and set initial state to start running.

   public class Monitor
    {
        public Monitor()
        {
        }

        public void MoveToNextState(StateBase nextState)
        {
            Console.WriteLine("Changing state...");
            this.CurrentState.Exit(this);
            this.CurrentState = nextState;
            this.CurrentState.Enter(this); 
        }

        public void Start()
        {
            this.CurrentState = new NotStartState();
            this.CurrentState.Enter(this); 
        }

        public StateBase CurrentState
        {
            get;
            set;
        }

开始使用状态机

        static void Main(string[] args)
        {
            Monitor m = new Monitor();
            m.Start(); 
        }