如何解开 Any 类型的可选值? [英] How to unwrap an optional value from Any type?

问题描述

给定一个 [Any] 数组，它混合了可选和非可选值，例如:

Given an array of [Any] that has a mix of optional and non optional values, e.g:

let int:Int? = 1
let str:String? = "foo"

let values:[Any] = [int,2,str,"bar"]

我们如何提取 Any 类型中 Optional 的值(如果有的话)，以便我们可以创建一个仅打印出值的通用打印函数.

How can we extract the value of the Optional in the Any type (if there is one) so we can create a generic print function that only prints out the values.

例如这个 printArray 函数遍历并打印每个元素:

E.g. this printArray function goes through and prints each element:

func printArray(values:[Any]) {
    for i in 0..<values.count {
        println("value[\(i)] = \(values[i])")
    }
}

printArray(values)

输出:

value[0] = Optional(1)
value[1] = 2
value[2] = Optional("foo")
value[3] = bar

我们如何更改它，使其仅打印底层值，以便在它是 Optional 时解开该值?例如:

How can we change it so it only prints the underlying value so that it unwraps the value if it's Optional? e.g:

value[0] = 1
value[1] = 2
value[2] = foo
value[3] = bar

<小时>

更新进度...

将参数更改为 [Any?] 时可以工作，例如:

let values:[Any?] = [int,2,str,"bar"]

func printArray(values:[Any?]) {
    for i in 0..<values.count {
        println("value[\(i)] = \(values[i]!)")
    }
}

printArray(values)

哪个将打印所需的:

value[0] = 1
value[1] = 2
value[2] = foo
value[3] = bar

但仍想看看我们如何从 Any 中解开 Optional，因为这是 MirrorType.value 返回的内容，因此很难提取 Optional 值，例如:

But would still like to see how we can unwrap an Optional from Any as this is what MirrorType.value returns making it difficult to extract the Optional value, e.g:

class Person {
    var id:Int = 1
    var name:String?
}

var person = Person()
person.name = "foo"

var mt:MirrorType = reflect(person)
for i in 0 ..< mt.count {
    let (name, pt) = mt[i]
    println("\(name) = \(pt.value)")
}

打印出来:

id = 1
name = Optional("foo")

当我需要时:

id = 1
name = foo

推荐答案

对于 Xcode 7 和 Swift 2:

For Xcode 7 and Swift 2:

func unwrap(any:Any) -> Any {

    let mi = Mirror(reflecting: any)
    if mi.displayStyle != .Optional {
        return any
    }

    if mi.children.count == 0 { return NSNull() }
    let (_, some) = mi.children.first!
    return some

}


let int:Int? = 1
let str:String? = "foo"
let null:Any? = nil
let values:[Any] = [unwrap(int),2,unwrap(str),"bar", unwrap(null)]

这会给你 [1, 2, "foo", "bar", {NSObject}]

将 NSNull() 更改为 nil 并将 unwrap func 的返回值更改为 Any? 将始终打开任何类型.

Change NSNull() to nil and the return value of unwrap func to Any? will always unwrap any type.

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