Unity C#编程优化——枚举

转自：

http://www.manew.com/thread-109311-1-1.html

Better C# Enums

1. 枚举：

public enum Planet {
    MERCURY,
    VENUS,
    EARTH,
    MARS,
    JUPITER,
    SATURN,
    URANUS,
    NEPTUNE,
    PLUTO // Pluto is a planet!!!
}

2.对应的质量

public float GetMass(Planet planet) {
    switch(planet) {
        case Planet.MERCURY:
            return 0.330;
        case Planet.VENUS:
            return 4.87f;
        case Planet.EARTH:
            return 5.97f;
        ...
        case Planet.PLUTO:
            return 0.0146f;
    }
}

3。要是多个属性就不方便:

行星直径又如何？另一个switch语句？密度怎么样？重力？逃跑速度？只要想想你将要维护的switch语句的数量。你可以争辩说，你可以使用一个Dictionary，但仍然笨重。每个数据的Dictionary都要映射？没门。

有一个更好的方法，我会告诉你如何。这可能已经是非Unity程序员的常识，但我想在我的博客中再次提出这个冗余的主题，对于那些可能不知道这一点的人来说，特别是初学者。我也想保持简单。

基本上，你可以使用类作为枚举。为什么用类？这确实表现的更好您可以存储任意数量的任意数据。您甚至可以存储例程或功能。你可以做很多事情。唯一的要求是它是不可变的，这意味着类一个实例的状态在整个程序期间都不能改变。以下是Planet枚举用类表示的一个版本：

public class Planet {
       // The different values
       public static readonly Planet MERCURY = new Planet(0, 0.330f, 4879, 5427, 3.7f);
       public static readonly Planet VENUS = new Planet(1, 4.87f, 12104, 5243, 8.9f);
       public static readonly Planet EARTH = new Planet(2, 5.97f, 12756, 5514, 9.8f);
       public static readonly Planet MARS = new Planet(3, 0.642f, 6792, 3933, 3.7f);
       public static readonly Planet JUPITER = new Planet(4, 1898.0f, 142984, 1326, 23.1f);
       public static readonly Planet SATURN = new Planet(5, 568.0f, 120536, 687, 9.0f);
       public static readonly Planet URANUS = new Planet(6, 86.8f, 51118, 1271, 8.7f);
       public static readonly Planet NEPTUNE = new Planet(7, 102.0f, 49528, 1638, 11.0f);
       public static readonly Planet PLUTO = new Planet(8, 0.0146f, 2370, 2095, 0.7f);
       // Use readonly to maintain immutability
       private readonly int id;
       private readonly float mass; // in 10^24 kg
       private readonly int diameter; // in km
       private readonly int density; // in kg/m^3
       private readonly float gravity; // in m/s^2
       // We use a private constructor because this should not be instantiated
       // anywhere else.
       private Planet(int id, float mass, int diameter, int density, float gravity) {
           this.id = id;
           this.mass = mass;
           this.diameter = diameter;
           this.density = density;
           this.gravity = gravity;
       }
       public int Id {
           get {
               return id;
           }
       }
       public float Mass {
           get {
               return mass;
           }
       }
       public int Diameter {
           get {
               return diameter;
           }
       }
       public int Density {
           get {
               return density;
           }
       }
       public float Gravity {
           get {
               return gravity;
           }
       }
   }

使用:

ship.TargetPlanet = Planet.NEPTUNE;
// Want to know the target planet's mass?
float mass = ship.TargetPlanet.Mass;
// Density?
int density = ship.TargetPlanet.Density;

5.我们已经消除了切换语句或字典来维护不同行星信息的需要。想要一个新的行星状态？只需添加一个新的成员变量并在实例化上指定它们。

如何从其他数据类型转换？喜欢说从int id转换为Planet实例？这很容易通常我为这些转换添加了一个公共和静态方法。例如：

public class Planet {
    // The different values
    public static readonly Planet MERCURY = new Planet(0, 0.330f, 4879, 5427, 3.7f);
    public static readonly Planet VENUS = new Planet(1, 4.87f, 12104, 5243, 8.9f);
    public static readonly Planet EARTH = new Planet(2, 5.97f, 12756, 5514, 9.8f);
    public static readonly Planet MARS = new Planet(3, 0.642f, 6792, 3933, 3.7f);
    public static readonly Planet JUPITER = new Planet(4, 1898.0f, 142984, 1326, 23.1f);
    public static readonly Planet SATURN = new Planet(5, 568.0f, 120536, 687, 9.0f);
    public static readonly Planet URANUS = new Planet(6, 86.8f, 51118, 1271, 8.7f);
    public static readonly Planet NEPTUNE = new Planet(7, 102.0f, 49528, 1638, 11.0f);
    public static readonly Planet PLUTO = new Planet(8, 0.0146f, 2370, 2095, 0.7f);
    // This can be used to loop through all planets
    public static Planet[] ALL = new Planet[] {
        MERCURY, VENUS, EARTH, MARS, JUPITER, SATURN, URANUS, NEPTUNE, PLUTO
    };
    // Converts the specified id to a Planet instance
    public static Planet Convert(int id) {
        for(int i = 0; i < ALL.Length; ++i) {
            if(ALL.Id == id) {
                return ALL;
            }
        }
        // return ALL[id] could also work here but what if a non sequential id is used?
        throw new Exception("Cannot convert {0} to a Planet.".FormatWith(id));
    }
    ...
}
// Usage
Planet planet = Planet.Convert(someIntPlanet);

也可以用继承

private static Dictionary<string, Planet> ALL = new Dictionary<string, Planet>() {
    { MERCURY.TextId, MERCURY },
    { VENUS.TextId, VENUS },
    { EARTH.TextId, EARTH },
    ...
    { PLUTO.TextId, PLUTO },
};
// Converts the specified string to a Planet instance
public static Planet Convert(string id) {
    return ALL[id];
}

您现在可以添加功能。你可以这样做：

Planet currentPlanet = Planet.VENUS;
currentPlanet.ApplyGravity(ship);
The coolest thing for me is you can specify different actions or behavior to the enum values. Something like this (It’s very contrived but you get the idea.):
public static readonly Planet EARTH = new Planet(2, 5.97f, 12756, 5514, 9.8f, delegate(Ship ship) {
    // Actions on land of ship
    ship.AddFood(1000);
    ship.RetireCrew();
    ship.RecruitNewCrew();
});
public static readonly Planet MARS = new Planet(3, 0.642f, 6792, 3933, 3.7f, delegate(Ship ship) {
    // Actions on land of ship
    ship.DeductFood(50);
    ship.Research();
    ship.Mine();
});

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