How to join array of optional integers to string?

Question

Given [Int?], need to build string from it.

This code snippet works

    let optionalInt1: Int? = 1
    let optionalInt2: Int? = nil

    let unwrappedStrings = [optionalInt1, optionalInt2].flatMap({ $0 }).map({ String($0) })
    let string = unwrappedStrings.joined(separator: ",")

But I don't like flatMap followed by map. Is there any better solution?

Answer 1

Here's another approach:

[optionalInt1, optionalInt2].flatMap { $0 == nil ? nil : String($0!) }

Edit: You probably shouldn't do this. These approaches are better, to avoid the !

[optionalInt1, optionalInt2].flatMap {
    guard let num = $0 else { return nil }
    return String(num)
}

or:

[optionalInt1, optionalInt2].flatMap { $0.map(String.init) }