如何为 swift 中的 nil 对象添加值

Question

我对您看到的这段代码有疑问。为什么它给我零价值，我怎么能弄清楚它是对的请帮我

struct NilControl{
    var name:String?
}

var k: NilControl?

print(k)
// nil -> Okey ı guess just like that
k?.name = "name"

print(k?.name)
// nil -> ı expect to see name but its still give me nil

Answer 1

查看内联评论以了解发生的情况：

struct NilControl{
    var name:String?
}

var k: NilControl? //you've defined k as NilControl? and not assigned it a value yet

print(k) //this will be nil, since k has not been set

k = NilControl() //this sets k to have a value (ie not nil), but its `name` is still nil at this point
k?.name = "name"

print(k?.name) //will print Optional("name")

如果您想在打印 name 之前对其进行一些 nil 检查，它可能看起来像这样：

k = NilControl(name: "name") //this sets k to have a value & assigns a name

if let k = k, let name = k.name {
    print(name)
}

如何为 swift 中的 nil 对象添加值

How can ı add value to nil object in swift

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xcode

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