Lambda表达式实现有限状态机

实现状态机有多种模式，其中最灵活而强大的方式是通过迁移表来实现，该方式的缺点之一是需要编写大量小块代码去支持迁移表。而在C#3.0中，可以以一种非常优雅的方式实现。除了有限状态机外,还有有限自动机,有限自动机一般用于分析字符。usingSystem;usingSystem.Collections.Generic;usingSystem.Linq;usingSystem.Text;namespaceStateMachine{ classPRogram { staticvoidMain(string[] args) { vardoor =newDoor(State.Open); while(true) { strings =Console.ReadLine(); Operationop =string.IsNullOrEmpty(s) ?Operation.Push :Operation.Pull; door.Process(op); } } } enumOperation { Push, Pull } enumState { Open, Closed } classDoor { publicStateState {get;set; } Dictionary<State,Dictionary<Operation,Action>> rule; publicDoor(Statestate) { this.State = state; rule =newDictionary<State,Dictionary<Operation,Action>>(); foreach(vareinEnum.GetValues(typeof(State))) { rule[(State)e] =newDictionary<Operation,Action>(); } InitOperationRule(); } voidInitOperationRule() { //正常操作 rule[State.Closed][Operation.Push] = () => {Console.WriteLine("门被推开了"); State =State.Open; }; rule[State.Open][Operation.Pull] = () => {Console.WriteLine("门被拉上了"); State =State.Closed; }; ////加入几种特殊情况的处理 //rule[State.Closed][Operation.Pull] = () => Console.WriteLine("门是关上的，拉了也白拉"); //rule[State.Open][Operation.Push] = () => Console.WriteLine("门是开的，不用推了，直接进去吧"); } publicvoidProcess(Operationop) { try { rule[State][op](); } catch(KeyNotFoundException) { Console.WriteLine(string.Format("门在{0}状态下不允许{1}操作", State, op)); } } }}从代码中可以看到，通过lambda表达式，可以简化迁移表的构造，并且更加直观。通过迁移表构造状态机的一种不足在于查询速度，在本例中每个操作都要进行两次查询才能进行状态转换操作。如果状态较多则非常费时，这里我把它改进了一下，使得每次操作只需要查询一次即可。 classDoorPlus { Statestate; publicStateState { get{returnstate; } set { if(state !=value) currentOpRule = rule[value]; state =value; } } Dictionary<Operation,Action> currentOpRule; Dictionary<State,Dictionary<Operation,Action>> rule; publicDoorPlus(Statestate) { this.State = state; rule =newDictionary<State,Dictionary<Operation,Action>>(); foreach(vareinEnum.GetValues(typeof(State))) { rule[(State)e] =newDictionary<Operation,Action>(); } currentOpRule = rule[State]; InitOperationRule(); } voidInitOperationRule() { //正常操作 rule[State.Closed][Operation.Push] = () => {Console.WriteLine("门被推开了"); State =State.Open; }; rule[State.Open][Operation.Pull] = () => {Console.WriteLine("门被拉上了"); State =State.Closed; }; ////加入几种特殊情况的处理 //rule[State.Closed][Operation.Pull] = () => Console.WriteLine("门是关上的，拉了也白拉"); //rule[State.Open][Operation.Push] = () => Console.WriteLine("门是开的，不用推了，直接进去吧"); } publicvoidProcess(Operationop) { try { currentOpRule[op](); } catch(KeyNotFoundException) { Console.WriteLine(string.Format("门在{0}状态下不允许{1}操作", State, op)); } } }