MVP architecture pattern example. Swift - ios

Question

I want to learn classic MVP architecture pattern and for this try to implement Weather app on Swift. I learned in theory how it should work but practically stuck on basic understanding. For now I have a model:
Model
class WeatherModel: Codable {
var name: String?
var main: Main?
}
class Main: Codable {
var temperature: Float?
var pressure: Int?
var humidity: Int?
private enum CodingKeys: String, CodingKey {
case temperature = "temp"
case pressure
case humidity
}
View
final class WeatherViewController: UIViewController {
#IBOutlet weak var cityTextField: UITextField!
#IBOutlet weak var temperatureLabel: UILabel!
#IBOutlet weak var pressureLabel: UILabel!
#IBOutlet weak var humidityLabel: UILabel!
private var presenter: WeatherPresenter!
// MARK: - Lifecycle
override func viewDidLoad() {
super.viewDidLoad()
presenter = WeatherPresenter()
cityTextField.delegate = self
presenter.delegate = self
}
#IBAction func buttonClicked(_ sender: Any) {
let city = cityTextField.text
if let city = city {
presenter.loadWeatherFor(city: city)
}
}
}
extension WeatherViewController: WeatherPresenterProtocol {
// MARK: - WeatherPresenterProtocol
func showWeather(data: WeatherModel) {
if let temperature = data.main?.temperature {
self.temperatureLabel.text = String(temperature)
}
if let pressure = data.main?.pressure {
self.pressureLabel.text = Constants.pressure + String(pressure)
}
if let humidity = data.main?.humidity {
self.humidityLabel.text = Constants.humidity + String(humidity)
}
}
}
Presenter
protocol WeatherPresenterProtocol: class {
func showWeather(data: WeatherModel) // ?
}
final class WeatherPresenter {
var model: WeatherModel!
weak var delegate: WeatherPresenterProtocol?
func loadWeatherFor(city: String) {
Network.shared.getWeather(city) { [weak self] (weather, error) in
DispatchQueue.main.async {
self?.model = weather
}
}
}
}
In Presenter I receive data from a Network Service but I can't understand how to update View with this data (how to implement protocol in Presenter) because View shouldn't know about model but in my case it will know( Any idea to implement classic MVP will be appreciated!
And second question: how to implement protocol in Presenter to get Model (as it is shown in the picture I've taken from https://www.youtube.com/watch?v=qzTeyxIW_ow)

Answer 1

Change
func showWeather(data: WeatherModel)
to
func showWeather(temperature: String, pressure: String, humidity: String)
Move the construction of these strings from the View to the Presenter. This way, the View remains ignorant of the model.
The Presenter should not speak directly to the full View, only to the protocol.

Answer 2

You can try this, in the MVP the presenter will take care of updating the view, so modify your presenter to have the view property. Here the view holds nothing but the WeatherController instance.
In terms of the MVP, the UIViewController subclasses are in fact the Views and not the Presenters.
class WeatherPresenter : WeatherViewPresenter {
unowned let view: WeatherView
let weather: WeatherModel
required init(view: WeatherView, weather: WeatherModel) {
self.view = view
self.weather = weather
}
func updateWeatherView() {
//...update properties on your weather view
self.view.setTemperature(self.weather.temperature)
}
}
For example,To update the temperature label, have a protocol to set the temperature value. You can have multiple methods to set multiple properties or have one for all of your UI elements in weather view.
protocol WeatherView: class {
func setTemperature(temp: String)
//same for pressure, humid etc
}
Now write a protocol for weather presenter
protocol WeatherViewPresenter {
init(view: WeatherView, weather: WeatherModel)
func updateWeatherView()
}
Now that you have the presenter setup for weather class, you would use it like
class WeatherViewController : UIViewController, WeatherView {
var presenter: WeatherViewPresenter!
override func viewDidLoad() {
super.viewDidLoad()
let model = //your weather model
presenter = WeatherPresenter(view: self, weather: model)
}
func setTemperature(temp: String) {
self.temperatureLabel.text = temp
}
}
After you get the data from weather, just call self.presenter.updateWeatherView() to update the weather view.
For more detailed info, please refer