在 Swift 中访问枚举关联值 [英] Accessing an Enumeration association value in Swift

问题描述

在这段代码中，我编写了一个非常无用的枚举，它定义了一个可能的带有 Int 或 Float 的 Number.

In this code I've written a really useless enum that defines a possible Number with Int or Float.

我无法理解如何访问我在关联中设置的值.如果我尝试打印它，我只会得到 (Enum Value)

I can't understand how can I access the value that I set with the association. If I try to print it I get just (Enum Value)

enum Number {
    case int (Int)
    case float (Float)
}

let integer = Number.int(10)
let float = Number.float(10.5)
println("integer is \(integer)")
println("float is \(float)")

推荐答案

该值与枚举的实例相关联.因此，要在没有开关的情况下访问它，您需要创建一个 getter 并使其显式可用.类似于以下内容:

The value is associated to an instance of the enumeration. Therefore, to access it without a switch, you need to make a getter and make it available explicitly. Something like below:

enum Number {
    case int(Int)
    case float(Float)

    func get() -> NSNumber {
        switch self {
        case .int(let num):
            return num
        case .float(let num):
            return num
        }
    }
}

var vInteger = Number.int(10)
var vFloat = Number.float(10.5)

println(vInteger.get())
println(vFloat.get())

也许将来会自动创建类似的东西，或者可以为语言添加更短的便利.

Maybe in the future something like that may be automatically created or a shorter convenience could be added to the language.

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