Swift MVVM Binding (Using Boxing) - ios

Question

I am trying to implement MVVM Architecture pattern using Boxing. I have done it simply by Adding the Boxing Class:
class Dynamic<T> {
typealias Listener = (T) -> Void
var listener: Listener?
func bind(listener: Listener?) {
self.listener = listener
}
func bindAndFire(listener: Listener?) {
self.listener = listener
listener?(value)
}
var value: T {
didSet {
listener?(value)
}
}
init(_ v: T) {
value = v
}}
And then In the ViewController I have referenced a ViewModel, this is my View Controller:
class SignUpViewController: UIViewController {
// UI Outlets
#IBOutlet weak var emailLoginTextField: FloatLabelTextField!
#IBOutlet weak var passwordLoginTextField: FloatLabelTextField!
var viewModel = AuthenticationViewModel()
override func viewDidLoad() {
super.viewDidLoad()
viewModel.user.email.bind{
self.emailLoginTextField.text = $0
}
}}
And This is my View Model:
class AuthenticationViewModel{
let defaults = UserDefaults.standard
let serviceManager = ServiceManager()
var user = User()
func signupUser(email : String?, password: String?){
let parameters : [String:String] = ["email":emailField, "password": password!, "system": "ios"]
serviceManager.initWithPOSTConnection(server: Utitlites.getServerName(), parameters: parameters, methodName: "/api/user/register", completion: { (responseData , errorMessage) -> Void in
let json = (responseData as AnyObject) as! JSON
print(json)
if ErrorHandling.handleErrorMessage(responseData: responseData).0 == true {
self.defaults.set("userId", forKey: json["user"]["id"].stringValue)
//self.userId.value = json["user"]["id"].stringValue
self.user = User(json: json)
}
})
}}
And this is my Model:
class User{
var id = Dynamic("")
var name = Dynamic("")
var email = Dynamic("")
init(){
}
init(json: JSON){
id.value = json["user"]["id"].stringValue
email.value = json["user"]["email"].stringValue
}}
My Question is:
MVVM Architecture wise, is it right to access the model using this line in the ViewController:
viewModel.user.email.bind{
self.emailLoginTextField.text = $0
}
Because I can see now that the View is accessing the Model which I think is not what MVVM Stands for. I need someone to clarify

Answer 1

The best practice to go about this (imo) and according to this raywanderlich video at 31:18 is to actually set the Model to be private, your VC doesn't need to know about it at all, only the ViewModel.
After that, set getters for the Model in the ViewModel like this:
var id: Dynamic<String> = Dynamic("")
var name: Dynamic<String> = Dynamic("")
var email: Dynamic<String> = Dynamic("")
And then, in your ViewModel also, set the User object to have a didSet notifier that will update the ViewModel's data accordingly:
private var user = User() {
didSet {
id = user.id
name = user.name
email = user.email
}
}
Now, you can access these properties only from the ViewModel instead of the Model directly:
viewModel.email.bind{
self.emailLoginTextField.text = $0
}
Oh, and don't forget to set the properties on the Model to be just regular strings ;)