【Swift 60秒】92 - Nil coalescing
0x00 Lesson
The nil coalescing
operator unwraps an optional and returns the value inside if there is one. If there isn’t a value - if the optional was nil
- then a default value is used instead. Either way, the result won’t be optional: it will either by the value from inside the optional or the default value used as a back up.
Here’s a function that accepts an integer as its only parameter and returns an optional string:
func username(for id: Int) -> {if id == 1 {return "Taylor Swift"} else {return nil}
}
If we call that with ID 15 we’ll get back nil
because the user isn’t recognized, but with nil coalescing we can provide a default value of “Anonymous” like this:
let user = username(for: 15) ?? "Anonymous"
That will check the result that comes back from the username()
function: if it’s a string then it will be unwrapped and placed into user
, but if it has nil
inside then “Anonymous” will be used instead.
0x01 我的小作品
欢迎体验我的作品之一:小五笔
五笔学习好帮手
App Store
搜索即可~