swift如何确定变量是否为可选 [英] swift How to determine if a variable is an optional

问题描述

我想知道变量是否是可选的

I want to know if a variable is an optional

我尝试以下方法，但失败

I try method below, but fail

func isOptional(v: Any) -> Bool {
    return v is Optional
}

推荐答案

作为一项学术练习(可以做还是应该做)，我想出了这一点:

As an academic exercise (can it be done vs. should it be done), I came up with this:

func isOptional(a: Any) -> Bool {
    return "\(a.dynamicType)".hasPrefix("Swift.Optional")
}

示例:

let name = "Fred"
let oname: String? = "Jones"
let age = 37
let oage: Int? = 38

let arr: [Any] = [name, oname, age, oage]

for item in arr {
    println("\(item) \(isOptional(item))")
}

输出:

Fred false
Optional("Jones") true
37 false
Optional(38) true

我建议在生产代码中使用它吗?否.我建议尽可能远离Any，我不敢打赌dynamicType的输出保持不变.

Would I recommend using this in production code? No. I recommend staying away from Any if at all possible, and I wouldn't bet on the output of dynamicType remaining the same.

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