Function Array> -> Optional>

Question

Here is what I\'m trying to do:

extension Array> {   
  func unwrap() -> Optional> {
    let a = self.flatMap         


        

Answer 1

findall's solution works, although I think it's more readable to just avoid generics for this case:

func unwrap(optionalArray : [Element?]) -> [Element]? {
    let unwrappedArray = optionalArray.flatMap { (a) -> [Element] in
        switch a {
        case Optional.Some(let x): return [x]
        case Optional.None: return []
        }
    }

    return unwrappedArray.count == optionalArray.count ? Optional.Some(unwrappedArray) : Optional.None
}

Usage:

let a = [Optional.Some(2), Optional.Some(3), Optional.Some(4)]
let b = [Optional.Some(1), Optional.None]

// Both are [Int]?
let unwrappedA = unwrap(a) // [2, 3, 4]
let unwrappedB = unwrap(b) // nil

See also: How to determine if a generic is an optional in Swift?