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Unity C#编程优化——枚举

日期：2019-01-25点击：467收藏

考虑下面关于行星枚举的这个例子：
public enum Planet {
MERCURY,
VENUS,
EARTH,
MARS,
JUPITER,
SATURN,
URANUS,
NEPTUNE,
PLUTO // Pluto is a planet!!!
}
起初，这样的定义还算好，直到需要产生一个行星的质量。所以我们做这样的事情：
// Returns the mass of the planet in 10^24 kg
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;
}
}

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;
}
}
}
为了保持不变性，所有成员变量应该是只读的。一旦他们被分配，他们将不能再被改变。这很重要，因为作为枚举，它的内部值不应该改变。然后将每个枚举值实现为该类的静态只读实例。

这是怎么用的？与正常枚举是一样的，如下使用：
// Use it like an enum
ship.TargetPlanet = Planet.NEPTUNE;
// Want to know the target planet's mass?
float mass = ship.TargetPlanet.Mass;
// Density?
int density = ship.TargetPlanet.Density;
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);

想从字符串ID转换？添加将保存此值的字符串成员变量。而不是使用诸如ALL []的数组，您可以使用如下所示的Dictionary：
private static Dictionary<string, planet="" style="color: rgb(34, 34, 34); font-family: 微软雅黑; font-size: 15px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration-style: initial; text-decoration-color: initial;"> 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];
}

您可以支持您喜欢的任何类型的转换。
还有更多的你可以做。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();
});

通过简单地将你的枚举变成一个类，你已经将它升级到更有组织的东西，而且更加功能强大。您也可以使用反射和继承等先进功能，但大多数情况下，您不需要。