Swift常数：Struct或Enum [英] Swift constants: Struct or Enum

问题描述

我不知道哪一个更好地定义常量。一个结构体或枚举。每次使用结构都会被复制？当我想到一个具有 static的结构时，这个常量在任何时候都不会被复制，在我看来。但是如果不会复制，那么我所需要的不重要？

I'm not sure which of both are better to define constants. A struct or a enum. A struct will be copied every time i use it or not? When i think about a struct with static let constants it makes no sense that it will copied all the time, in my opinion. But if it won't copied then it doesn't matter what I take?

结构或枚举的选择有哪些优点？

What advantages does the choice of a struct or enum?

Francisco表示使用Struct's。

Ray Wunderlich说使用Enum的。但是我缺乏理由。

推荐答案

结构和枚举都可以正常工作。例如，

Both structs and enumerations work. As an example, both

struct PhysicalConstants {
    static let speedOfLight = 299_792_458
    // ...
}

和

enum PhysicalConstants {
    static let speedOfLight = 299_792_458
    // ...
}

工作并定义静态属性 PhysicalConstants.speedOfLight 。

struct 和枚举是值类型，因此也适用于枚举。但是这是$ / $> $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $的类型本身，而不是这种类型的实例。

Both struct and enum are value types so that would apply to enumerations as well. But that is irrelevant here because you don't have to create a value at all: Static properties (also called type properties) are properties of the type itself, not of an instance of that type.

如链接文章所述：

使用无病例枚举的优点是它不能被意外实例化，并且可以作为纯名称空间使用。

The advantage of using a case-less enumeration is that it can't accidentally be instantiated and works as a pure namespace.

所以对于一个结构，

let foo = PhysicalConstants()

创建一个（无用的）类型为 PhysicalConstants 但
为无法编译的无病例枚举：

creates a (useless) value of type PhysicalConstants, but for a case-less enumeration it fails to compile:

let foo = PhysicalConstants()
// error: 'PhysicalConstants' cannot be constructed because it has no accessible initializers

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