import Foundation

protocol Receivable {
    init?(from: Data)
}

extension Receivable where Self: Decodable {
    init?(from jsonData: Data) {
        guard let decoded = try? JSONDecoder().decode(Self.self, from: jsonData) else { return nil }
        self = decoded
    }
}

extension Array where Element: Receivable & Decodable {
    init?(from jsonData: Data) {
        guard let decoded = try? JSONDecoder().decode(Array<Element>.self, from: jsonData) else { return nil }
        self = decoded
    }
}

struct TestObject2: Codable, Receivable {
    let id: String
    let pass: String
}

// TEST
let jsonData = "{\"id\":\"hi\", \"pass\":\"omg\"}".data(using: .utf8)!
// try! JSONEncoder().encode(TestObject2(id: "hi", pass: "omg"))
print(TestObject2(from: jsonData))

let jsonArrayData = "[{\"id\":\"hi\", \"pass\":\"omg\"}, {\"id\":\"bye\", \"pass\":\"good\"}]".data(using: .utf8)!
//try! JSONEncoder().encode([TestObject2(id: "hi", pass: "omg"), TestObject2(id: "hi2", pass: "omg!!!")])
print([TestObject2](from: jsonArrayData))