optionalUnwrap.swift

protocol OptionalType {
  associatedtype W
  var optional: W? { get }
}

extension Optional: OptionalType {
  typealias W = Wrapped
  var optional: W? { return self }
}

extension Array where Element: OptionalType {
  func unwrap() -> [Element.W] {
    return flatMap { $0.optional }
  }
}