protocol DictionaryRepresentable: class {
    associatedtype SelfType = Self
    func asDictionary() -> [String:Any]
    static func from(dictionary: [String:Any]) -> SelfType?
    static func from(dictionaries: [[String:Any]]) -> [SelfType]
}

extension Array where Element:DictionaryRepresentable {
    func asDictionaries() -> [[String:Any]] {
        return self.map({ (representable) -> [String:Any] in
            return representable.asDictionary()
        })
    }
}


// Here's what I wanted to do, but can't.

extension Array where Element == [String:Any] {
    func asType<Q:DictionaryRepresentable>() -> [Q] {
        return self.flatMap({ (dictionary) -> Q? in
            return Q.from(dictionary: dictionary)
            //Xcode says: "Cannot convert value of type 'Q.SelfType?' to closure result type '_?'"
        })
    }
}


// So I resorted to adding that third protocol method,
// and at least gave it a default implementation, as seen below:

extension DictionaryRepresentable {
    static func from(dictionaries: [[String:Any]]) -> [SelfType] {
        return dictionaries.flatMap { (dict) -> SelfType? in
            return self.from(dictionary: dict)
        }
    }
}