我应该使用什么模式来表达层次枚举？

Question

我正在尝试使用API​​在给定时间发布值(值和时间元组).这些样本将由数据查看器(例如图表)使用.

我想将值与数量和单位相关联,例如以米为单位的长度.这样我的"观众"可以适当地缩放它.

我正在寻找一种分层枚举,如下所示:

enum Quantity
{
   Mass.Kg,
   Mass.g,
   Length.m,
   Length.mm
}

但这在C#中不存在.

我不确定表达这个的最佳模式,我想出了以下内容.是否有一种公认的或更好的方法来做到这一点？

using System;
using Moq;

namespace ConsoleApplication26
{
    class Program
    {
        static void Main(string[] args)
        {
            //use a Mock to play with the API
            Mock<ITelemetryPublisherFactory> mockTelemetryPublisherFactory = new Mock<ITelemetryPublisherFactory>();
            var telemetryPublisherFactory = mockTelemetryPublisherFactory.Object;

            //example usages
            var massTelemetryPublisher = telemetryPublisherFactory.GetChannelSamplePublisher<Double>("My Mass", Mass.Kg);
            massTelemetryPublisher.PublishChannelSampleAtTimeNow(83.4);                        

            var lengthTelemetryPublisher = telemetryPublisherFactory.GetChannelSamplePublisher<Int32>("My Height", Length.?m);
            lengthTelemetryPublisher.PublishChannelSampleAtTimeNow(1800000);      

            //10 years time..
            lengthTelemetryPublisher.PublishChannelSampleAtTimeNow(1800000);
            massTelemetryPublisher.PublishChannelSampleAtTimeNow(120.1);                        
        }
    }

    public interface ITelemetryPublisherFactory
    {
        ITelemetryPublisher<T> GetChannelSamplePublisher<T>(String channelName, Quantity quantity);
    }

    public interface ITelemetryPublisher<T>
    {
        void PublishChannelSampleAtTimeNow(T sampleValue);
    }

    public abstract class Quantity {}

    public class Mass : Quantity
    {
        private enum Unit
        {
            g,
            Kg
        }

        private readonly Unit _unit;

        private Mass(Unit unit)
        {
            _unit = unit;
        }

        public static Quantity Kg {get { return new Mass(Unit.Kg); }}
        public static Quantity g { get { return new Mass(Unit.g); } }

        public override string ToString()
        {
            return String.Format("Mass.{0}", _unit);
        }
    }

    public class Length : Quantity
    {
        private enum Unit
        {
            m,
            mm,
            ?m,
            beardSecond
        }

        private readonly Unit _unit;

        private Length(Unit unit)
        {
            _unit = unit;
        }

        public static Quantity m { get { return new Length(Unit.m); } }
        public static Quantity mm { get { return new Length(Unit.mm); } }
        public static Quantity ?m { get { return new Length(Unit.?m); } }
        public static Quantity beardSecond { get { return new Length(Unit.beardSecond); } }

        public override string ToString()
        {
            return String.Format("Length.{0}", _unit);
        }        
    }    
}

Answer 1

我认为最好Unit为计量单位创建一个类，Quantity并将计量单位与金额关联起来。查看该想法的数量模式。由于您还想记录测量单位的“类型”，因此您可以创建一个UnitType记录该信息的类：

public sealed partial class UnitType {
  public string Name { get; private set; }
  public UnitType(string name) {
    Name = name;
  }
}

public sealed partial class Unit {
  public string Name { get; private set; }
  public UnitType Type { get; private set; }
  public Unit(string name, UnitType type) {
    Name = name;
    Type = type;
  }
}

（您应该通过覆盖Equalsand使它们成为正确的值类型GetHashCode）

该类Unit可以扩展以提供例如转换、复合单元、格式化和解析。

然后，您可以在类中定义常见情况：

public partial class UnitType {
  public static readonly UnitType Mass = new UnitType("Mass");
  public static readonly UnitType Length = new UnitType("Length");
}

public partial class Unit {
  public static readonly Unit Grams = new Unit("g", UnitType.Mass);
  public static readonly Unit Kilos = new Unit("kg", UnitType.Mass);
  // ...
}

或者用静态类定义你的“层次结构”：

public static class Mass {
  public static readonly UnitType Type = new UnitType("Mass");

  public static readonly Unit Grams = new Unit("g", Type);
  public static readonly Unit Kilos = new Unit("kg", Type);
  ...
}

public static class Length ...

该类Quantity也将是一个不可变的值类型（仅显示其用法）：

var eniacWeight = new Quantity(27, Mass.Tons);

或者您可以使用扩展方法来创建Quantitys：

var eniacWeight = 27.Tons();

（来自埃尼阿克）