Swift:添加可选的Ints [英] Swift: adding optionals Ints

问题描述

我声明以下内容:

var x:Int?
var y:Int?

，我想要第三个变量z，它包含x和y的总和.大概是x& y是可选的，z也必须是可选的:

and I'd like a third variable z that contains the sum of x and y. Presumably, as x & y are optionals, z must also be an optional:

var z:Int? = x + y

但这会产生一个编译器错误可选类型'Int?'的值没有解包；您的意思是使用'！'或'?'"

but this gives a complier error "value of optional type 'Int?' not unwrapped; did you mean to use '!' or '?'"

如果我打开x& y:

If I unwrap x & y:

var z:Int? = x! + y!

我收到一个运行时错误x& y为nil，所以不能解包.

I get a run-time error as x & y are nil, so can't be unwrapped.

我可以达到预期的结果，

I can achieve the desired result as follows:

var z:Int?

if let x1 = x {
    if let y1 = y {
       z = x1+y1
    }
}

但是将2个整数加在一起似乎有点冗长！有没有更好的方法来实现这一目标?

but this seems a bit verbose for adding together 2 integers! Is there a better way of achieving this?

推荐答案

这是我的看法，我认为它更干净:

Here is my take, I think it's cleaner:

let none:Int? = nil
let some:Int? = 2

func + (left: Int?, right:Int?) -> Int? {
    return left != nil ? right != nil ? left! + right! : left : right
}

println(none + none)
println(none + some)
println(some + none)
println(some + some)
println(2 + 2)

结果如下:

nil
Optional(2)
Optional(2)
Optional(4)
4

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