Mapping with filtering nil

gistfile1.swift

let values = [ "1", "foo", "3" ]

// Swift 1.2

extension Array {
    func filterMap(@noescape transform: T -> U?) -> [U] {
        var results = [U]()
        for x in self {
            if let mapped = transform(x) {
                results.append(mapped)
            }
        }
        return results
    }
}

let numbers1: [Int?] = values.map { $0.toInt } // [ 1, nil, 3 ]
let numbers2: [Int] = values.filterMap { $0.toInt } // [ 1, 3 ]

// Swift 2

let numbers: [Int] = values.flatMap { Int($0) } // [ 1, 3 ]