如何在Swift中为此通用数据类型添加扩展名？

Question

I'm using the Mapper library with Swift for JSON.

To get it into a variable you do something like:

try firstName = map.from("first_name")

With autocomplete I can see the result of map.from is a value of type T which is a generic I think.

I want to add a nilIfEmpty method like map.from(value).nilIfEmpty() so that if the json is just "" I'll have it be nil. It's a lot more compact than map.from(value) == "" ? nil : map.from(value) map.from(value) == "" ? nil : map.from(value)

How would I write this though?

Answer 1

You could just extend String :

extension String {
    func nilIfEmpty() {
        return self.isEmpty ? nil : self
    }
}

map.from(value).nilIfEmpty()