How to use swift flatMap to filter out optionals from an array

Question

I\'m a little confused around flatMap (added to Swift 1.2)

Say I have an array of some optional type e.g.

let possibles:[Int?] = [nil, 1, 2, 3, nil, nil         


        

Answer 1

Related to the question. If you are applying flatMap to an optional array, do not forget to optionally or force unwrap your array otherwise it will call flatMap on Optional and not objects conforming to Sequence protocol. I made that mistake once, E.g. when you want to remove empty strings:

var texts: [String]? = ["one", "two", "", "three"] // has unwanted empty string

let notFlatMapped = texts.flatMap({ $0.count > 0 ? $0 : nil })
// ["one", "two", "", "three"], not what we want - calls flatMap on Optional

let flatMapped = texts?.flatMap({ $0.count > 0 ? $0 : nil })
// ["one", "two", "three"], that's what we want, calls flatMap on Array