// Create models from a JSON dictionary
let jsonSignalProducer: SignalProducer<Any, NSError> = // ...
jsonSignalProducer.mapToType(User).startWithResult { result in
    // use the decoded User model
    let user: User? = result.value
}

// Create array of models from array of JSON dictionaries
let jsonSignalProducer: SignalProducer<Any, NSError> = // ...
jsonSignalProducer.mapToTypeArray(Task).startWithResult { result in
    // use the decoded array of Task models
    let tasks: [Task]? = result.value
}

struct Dog {
    let name: String
}

extension Dog: Encodeable {
    func encode() -> [String: Any] {
        return ["name": name]
    }
}

struct User {
    let id: String
    let name: String?
    let dog: Dog
}

extension User: Encodeable {
    func encode() -> [String: Any] {
        return [
            "id": id,
            "name": name ?? Encodeable.null,
            "dog": dog.encode()
        ]
    }
}

let dog = Dog(name: "Waldo")
let user = User(id: "1", name: nil, dog: dog)
let encoded = user.encode() // ["id": "1", "name": NSNull, "dog": ["name": "Waldo"]]