.NET(C#) 设计模式 解释器模式

解释器模式（Interpreter Pattern）

解释器模式（Interpreter Pattern）是一种行为型模式，定义了一个解释器，来解释给定语言和文法的句子。其实质是把语言中的每个符号定义成一个（对象）类，从而把每个程序转换成一个具体的对象树。解释器模式的作用很强大，它使得改变和扩展文法变得容易，很多编译器，包括文本编辑器、网页浏览器及VRML都应用解释器模式。因文句会分析成树结构，解释器需要递归访问它，则效率会受影响。程序开发时会有所体会，编译整个工程源码耗费时间都比较长。

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;namespace ConsoleApplication{    //一般每个接口或类都写在单独的.cs文件中    //本示例为了执行查看方便才写在一起    /// 
    /// 解释器抽象类    /// 
    abstract class AbstractionExpression    {        public abstract string Interpret();    }    /// 
    /// 用于解释具体的某个指令    /// 
    class TerminalExpression : AbstractionExpression    {        AbstractionExpression _Dir, _RunMode, _Dis;        public TerminalExpression(AbstractionExpression dir, AbstractionExpression runMode, AbstractionExpression dis)        {            this._Dir = dir;            this._RunMode = runMode;            this._Dis = dis;        }        public override string Interpret()        {            return string.Concat(_Dir.Interpret(), _RunMode.Interpret(), _Dis.Interpret());        }    }    /// 
    /// 用于将终结符表达式连接起来    /// 
    class NonTerminalExpression : AbstractionExpression    {        AbstractionExpression _Left, _Right;        public NonTerminalExpression(AbstractionExpression left, AbstractionExpression right)        {            this._Left = left;            this._Right = right;        }        public override string Interpret()        {            return $"{this._Left.Interpret()}然后{ this._Right.Interpret()} ";        }    }    /// 
    /// 终结符表达式中需要用到的表达式    /// 
    class DirExpression : AbstractionExpression    {        string _Dir;        public DirExpression(string dir)        {            this._Dir = dir;        }        public override string Interpret()        {            if (this._Dir == "up")            {                return "向上";            }            else if (this._Dir == "down")            {                return "向下";            }            else if (this._Dir == "left")            {                return "向左";            }            else if (this._Dir == "right")            {                return "向右";            }            else            {                return "方向错误";            }        }    }    class RunModeExpression : AbstractionExpression    {        public string _RunMode;        public RunModeExpression(string runMode)        {            this._RunMode = runMode;        }        public override string Interpret()        {            if (this._RunMode == "move")            {                return "移动";            }            else if (this._RunMode == "run")            {                return "快速移动";            }            else            {                return "运动模式错误";            }        }    }    class DisExpression : AbstractionExpression    {        string _Dis;        public DisExpression(string dis)        {            this._Dis = dis;        }        public override string Interpret()        {            return $"距离为{this._Dis }";        }    }    /// 
    /// 上下文环境类    /// 
    public class HandleExpression    {        Stack stack = new Stack();//使用栈类实现递归        AbstractionExpression _dir, _runMode, _dis;        AbstractionExpression allExpression;        public void Operate(string expression)        {            string[] str = expression.Split(' ');            for (int i = 0; i < str.Length; i++)            {                if (str[i] == "and")                {                    AbstractionExpression left = stack.Pop();                    _dir = new DirExpression(str[++i]);                    _runMode = new RunModeExpression(str[++i]);                    _dis = new DisExpression(str[++i]);                    AbstractionExpression right = new TerminalExpression(_dir, _runMode, _dis);                    AbstractionExpression endExpression = new NonTerminalExpression(left, right);                    stack.Push(endExpression);                }                else                {                    _dir = new DirExpression(str[i]);                    _runMode = new RunModeExpression(str[++i]);                    _dis = new DisExpression(str[++i]);                    AbstractionExpression endExpression = new TerminalExpression(_dir, _runMode, _dis);                    stack.Push(endExpression);                }            }            allExpression = stack.Pop();//弹出所有表达式        }        public string InterpretAll()        {            return allExpression.Interpret();        }    }    class Program    {        static void Main(string[] args)        {            HandleExpression handleExpression = new HandleExpression();            string expression = "up move 230 and down run 640";            handleExpression.Operate(expression);            string result = handleExpression.InterpretAll();            Console.WriteLine(result);            Console.ReadKey();        }    }}