解譯器模式(Interpreter)

• 給定一個語言，定義它的文法的一種表示，並定義一個解釋器，解釋器使用該表示來解釋語言中的句子。
• 當有一個語言需要解譯執行，並且你可將該語言中的句子表示為一個抽象語法樹時，可使用解譯器模式。

基本架構圖

實例架構圖

using System;
using System.Configuration;
using System.Reflection;

namespace DPExample
{
    // 演奏內容
    public class PlayContext
    {
        private string text;
        public string 演奏文字
        {
            get { return text; }
            set { text = value; }
        }
    }

    // 運算式
    abstract class Expression
    {
        public void 解譯器(PlayContext context)
        {
            if (context.演奏文字.Length == 0)
                return;
            else
            {
                string playKey = context.演奏文字.Substring(0, 1);
                context.演奏文字 = context.演奏文字.Substring(2);

                double playValue = Convert.ToDouble(context.演奏文字.Substring(0, context.演奏文字.IndexOf(" ")));
                context.演奏文字 = context.演奏文字.Substring(context.演奏文字.IndexOf(" ") + 1);

                執行(playKey, playValue);
            }
        }

        public abstract void 執行(string key, double value);
    }

    // 音符
    class Note : Expression
    {
        public override void 執行(string key, double value)
        {
            string note = "";
            switch (key)
            {
                case "C":
                    note = "1";
                    break;
                case "D":
                    note = "2";
                    break;
                case "E":
                    note = "3";
                    break;
                case "F":
                    note = "4";
                    break;
                case "G":
                    note = "5";
                    break;
                case "A":
                    note = "6";
                    break;
                case "B":
                    note = "7";
                    break;
            }
            Console.Write ("{0} ", note);
        }
    }

    // 音階
    class Scale : Expression
    {
        public override void 執行(string key, double value)
        {
            string scale = "";
            switch (Convert.ToInt32(value))
            {
                case 1:
                    scale = "低音";
                    break;
                case 2:
                    scale = "中音";
                    break;
                case 3:
                    scale = "高音";
                    break;
            }

            Console.Write ("{0} ", scale);
        }
    }

    // 音速
    class Speed : Expression
    {
        public override void 執行(string key, double value)
        {
            string speed;
            if (value < 500)
                speed = "快速";
            else if (value >= 1000)
                speed = "慢速";
            else
                speed = "中速";

            Console.Write ("{0} ", speed);
        }
    }

    // 運算式工廠
    class ExpressionFactory
    {
        private static readonly string MusicAssemblyName = "DPExample";
        private static string concreteExpression;

        public static Expression createExpression (string str)
        {
            concreteExpression = ConfigurationManager.AppSettings["MUSIC_" + str];

            string className = MusicAssemblyName + "." + concreteExpression;

            return (Expression)Assembly.Load(MusicAssemblyName).CreateInstance(className);
        }
    }
}

一般版本

using System;

namespace DPExample
{
    public class Program
    {
        static void Main()
        {
            PlayContext context = new PlayContext();

            Console.WriteLine("上海灘：");
            context.演奏文字 = "T 500 O 2 E 0.5 G 0.5 A 3 E 0.5 G 0.5 D 3 E 0.5 G 0.5 A 0.5 O 3 C 1 O 2 A 0.5 G 1 C 0.5 E 0.5 D 3 ";

            Expression expression = null;
            try
            {
                while (context.演奏文字.Length > 0)
                {
                    string str = context.演奏文字.Substring(0, 1);
                    switch (str)
                    {
                        case "O":
                            expression = new Scale();
                            break;
                        case "T":
                            expression = new Speed();
                            break;
                        case "C":
                        case "D":
                        case "E":
                        case "F":
                        case "G":
                        case "A":
                        case "B":
                        case "P":
                            expression = new Note();
                            break;
                    }

                    expression.解譯器(context);
                }
            } catch (Exception ex)
            {
                Console.WriteLine (ex.Message);
            }
        }

    }
}

透過簡單工廠+反射修正

using System;

namespace DPExample
{
 public class Program
 {
  static void Main()
        {
            PlayContext context = new PlayContext();

            Console.WriteLine("上海灘：");
            context.演奏文字 = "T 500 O 2 E 0.5 G 0.5 A 3 E 0.5 G 0.5 D 3 E 0.5 G 0.5 A 0.5 O 3 C 1 O 2 A 0.5 G 1 C 0.5 E 0.5 D 3 ";

            Expression expression = null;
            try
            {
                while (context.演奏文字.Length > 0)
                {
                    string str = context.演奏文字.Substring(0, 1);

                    expression = ExpressionFactory.createExpression(str);
                    expression.解譯器(context);
                }
            } catch (Exception ex)
            {
                Console.WriteLine (ex.Message);
            }
  }

 }
}