Is there a pretty way to increment an optional Int?

问题

I want to increment an Int?
Currently I have written this :

return index != nil ? index!+1 : nil

Is there some prettier way to write this ?

回答1:

For the sake of completeness, Optional has a map() method:

/// If `self == nil`, returns `nil`.  Otherwise, returns `f(self!)`.
@warn_unused_result
@rethrows public func map<U>(@noescape f: (Wrapped) throws -> U) rethrows -> U?

Therefore

index != nil ? index! + 1 : nil

is equivalent to

index.map { $0 + 1 }

回答2:

You can call the advanced(by:) function using optional chaining:

return index?.advancedBy(1)

Note: This works for any Int, not just 1.

---

If you find yourself doing this many times in your code, you could define your own + operator that adds an Int to an Int?:

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

Then you could just do:

return index + 1

回答3:

You can optionally call any method on an optional by prepending the call with a question mark, and this works for postfix operators too:

return index?++

More generally you can also write:

index? += 1; return index

来源：https://stackoverflow.com/questions/33804794/is-there-a-pretty-way-to-increment-an-optional-int