Unity实现设计模式——解释器模式

解释器模式（Interpreter Pattern）是一种按照规定语法进行解析的模式，现实项目中用得较少。给定一门语言，定义它的文法的一种表示，并定义一个解释器，该解释器使用该表示来解释语言中的句子。
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下面用一个例子演示：将罗马文字转换为十进制的格式

1.Context

    class Context{private string _input;private int _output;// Constructorpublic Context(string input){this._input = input;}// Gets or sets inputpublic string Input{get { return _input; }set { _input = value; }}// Gets or sets outputpublic int Output{get { return _output; }set { _output = value; }}}

2.Expression

解释器基类

    abstract class Expression{//"MCMXXVIII";public void Interpret(Context context){if (context.Input.Length == 0)return;if (context.Input.StartsWith(Nine())){context.Output += (9 * Multiplier());context.Input = context.Input.Substring(2);}else if (context.Input.StartsWith(Four())){context.Output += (4 * Multiplier());context.Input = context.Input.Substring(2);}else if (context.Input.StartsWith(Five())){context.Output += (5 * Multiplier());context.Input = context.Input.Substring(1);}while (context.Input.StartsWith(One())){context.Output += (1 * Multiplier());context.Input = context.Input.Substring(1);}}public abstract string One();public abstract string Four();public abstract string Five();public abstract string Nine();public abstract int Multiplier();}

3.ThousandExpression

千位数字解释器

    class ThousandExpression : Expression{public override string One() { return "M"; }public override string Four() { return " "; }public override string Five() { return " "; }public override string Nine() { return " "; }public override int Multiplier() { return 1000; }}

4.HundredExpression

百位数字解释器

    class HundredExpression : Expression{public override string One() { return "C"; }public override string Four() { return "CD"; }public override string Five() { return "D"; }public override string Nine() { return "CM"; }public override int Multiplier() { return 100; }}

5.TenExpression

十位数字解释器

    class TenExpression : Expression{public override string One() { return "X"; }public override string Four() { return "XL"; }public override string Five() { return "L"; }public override string Nine() { return "XC"; }public override int Multiplier() { return 10; }}

6.OneExpression

个位数字解释器

    class OneExpression : Expression{public override string One() { return "I"; }public override string Four() { return "IV"; }public override string Five() { return "V"; }public override string Nine() { return "IX"; }public override int Multiplier() { return 1; }}

7.测试

    public class InterpreterExample1 : MonoBehaviour{void Start(){string roman = "MCMXXVIII";Context context = new Context(roman);// Build the 'parse tree'List<Expression> tree = new List<Expression>();tree.Add(new ThousandExpression());tree.Add(new HundredExpression());tree.Add(new TenExpression());tree.Add(new OneExpression());// Interpretforeach (Expression exp in tree){exp.Interpret(context);}Debug.Log(roman+" = "+ context.Output);}}