Extension of type Array with constraints cannot have an inheritance clause - swift 2 [duplicate]

Question

In swift 2 I want to extend Array type. I have a JSONDecodable protocol. What i want to say to compiler is conform Arrayto protocol JSONDecodable if elements of Array are also JSONDecodable. Here is the code:

public protocol JSONDecodable {
    static func createFromJSON(json: [String: AnyObject]) throws -> Self
}

extension Array: JSONDecodable where Element: JSONDecodable {

}

But compiler gives the error: "Extension of type Array with constraints cannot have an inheritance clause"

So is there any other way to accomplish this kind of behavior?

Answer 1

how about little type erasure? It should do the tick

protocol JSONDecodable {
    init(json: JSON) throws
}

While Swift 3 doesn't allow do like extension

extension Array: JSONDecodable where Element: JSONDecodable

but its possible to do:

extension Array: JSONDecodable {
    init(json: JSON) throws {
        guard let jsonArray = json.array,
            let decodable = Element.self as? JSONDecodable.Type else {
                throw JSONDecodableError.undecodable
        } 

        self = jsonArray.flatMap { json in
            let result: Element? = (try? decodable.init(json: json)) as? Element
            return result
        }
    }
}