Swift 2.1 Array Extension objectsAtIndexes

Question

I'm trying to extend an array to return only objects at certain indexes. The map function seemed to be the best choice for me here.

extension Array {

    func objectsAtIndexes(indexes: [Int]) -> [Element?]? {
        let elements: [Element?] = indexes.map{ (idx) in
            if idx < self.count {
                return self[idx]
            }
            return nil
        }.filter { $0 != nil }
        return elements
    }
}

let arr = ["1", "2", "3", "4", "5"]
let idx = [1,3,5]

let x = arr.objectsAtIndexes(idx) //returns: [{Some "2"}, {Some "4"}]

I'm getting a EXC_BAD_INSTRUCTION error when I try to cast the result to a string array:

let x = arr.objectsAtIndexes(idx) as? [String]

Is there any way I can return an array of non-optionals? I've tried to return [Element]? from the extension function. This throws the same error.

score 2 · Accepted Answer · answered Nov 26 '15 at 23:12

The following code solves the problem for Swift2.1 using the flatmap function.

extension Array {

    func objectsAtIndexes(indexes: [Int]) -> [Element] {
        let elements: [Element] = indexes.map{ (idx) in
            if idx < self.count {
                return self[idx]
            }
            return nil
            }.flatMap{ $0 }
        return elements
    }
}

Swift 2.1 Array Extension objectsAtIndexes

1 Answers1