Cannot transfer Data from VC1 to VC2 using protocols in Swift - ios

Question

well, im using 2 VCs, one with a textField where the user inputs the CityName, and another VC where it takes care of all the UI elements(like the temp, cityname, etc..), now I use also a NetWorkManager to take care of all the networking&JSON stuff.
the problem is im trying to transfer the data from the NetWorkManager to VC1 but for some reason the delegate aint working :( - basically the road should be like this : VC2 -> NetWorkManager -> VC1.
Here's my Code:
import Foundation
protocol NetworkManagerDelegate {
func didUpdateWeather(weather: WeatherModel)
}
struct NetworkManager {
let weatherURL = "https://api.openweathermap.org/data/2.5/weather?appid=2da9980c9a43e21c2cdb1f28316d151d&units=metric"
var delegate: NetworkManagerDelegate?
func fetchWeather(cityName: String) {
let urlString = "\(weatherURL)&q=\(cityName)"
performRequest(urlString: urlString)
}
func performRequest(urlString: String) {
if let url = URL(string: urlString) {
let session = URLSession(configuration: .default)
let task = session.dataTask(with: url) { (data, respone, error) in
if error != nil {
print(error!)
}
if let safeData = data {
if let weather = self.parseJSON(weatherData: safeData) {
print("Im not nil")
self.delegate?.didUpdateWeather(weather: weather)
}
}
}
task.resume()
}
}
func parseJSON(weatherData: Data) -> WeatherModel? {
let decoder = JSONDecoder()
do {
let decodedData = try decoder.decode(WeatherDataModel.self, from: weatherData)
let id = decodedData.weather[0].id
let cityName = decodedData.name
let temp = decodedData.main.temp
let weather = WeatherModel(conditionId: id, cityName: cityName ,temperatrue: temp)
print("Temp is: \(weather.temperatrueString)")
return weather
} catch {
print(error)
return nil
}
}
}
VC2:
import UIKit
import Foundation
class WeatherByCityController: UIViewController, UITextFieldDelegate {
// func didUpdateWeather(weather: WeatherModel) {
// print("Hi")
// }
//
#IBOutlet weak var cityTextField: UITextField!
#IBOutlet weak var updateWeatherBtn: UIButton!
var netWorkManager = NetworkManager()
override func viewDidLoad() {
super.viewDidLoad()
// netWorkManager.delegate = self
cityTextField.delegate = self
}
#IBAction func closeButtonTapped(_ sender: UIButton) {
dismiss(animated: true, completion: nil)
}
#IBAction func updateWeatherByCityTapped(_ sender: UIButton) {
//Calling delegate to update the City:
//Dismiss the VC:
dismiss(animated: true, completion: nil)
}
func textFieldShouldReturn(_ textField: UITextField) -> Bool {
cityTextField.endEditing(true)
return true
}
func textFieldDidEndEditing(_ textField: UITextField) {
if let city = cityTextField.text {
netWorkManager.fetchWeather(cityName: city)
}
cityTextField.text = ""
}
}
VC1:
import UIKit
import Foundation
import CoreLocation
class WeatherScreen: UIViewController,NetworkManagerDelegate {
//Objects outlets:
#IBOutlet weak var conditionIcon: UIImageView!
#IBOutlet weak var tempLabel: UILabel!
#IBOutlet weak var cityLabel: UILabel!
//TableView Outlet:
#IBOutlet weak var tableView: UITableView!
#IBOutlet weak var segeControl: UISegmentedControl!
var models = [DailyWeatherEntry]()
var hourlyModels = [HourlyWeatherEntry]()
var netWorkManager = NetworkManager()
override func viewDidLoad() {
netWorkManager.delegate = self
tableView.register(HourlyTableViewCell.nib(), forCellReuseIdentifier: HourlyTableViewCell.identifier)
tableView.dataSource = self
}
override func viewWillAppear(_ animated: Bool) {
// Load things once the view will appear
}
#IBAction func locationBtnTapped(_ sender: UIButton) {
//Asking the user for a permission for using his location:
}
func didUpdateWeather(weather: WeatherModel) {
print("Hi")
}
}
extension WeatherScreen: UITableViewDataSource {
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return 2
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
//creating the cell:
let cell = tableView.dequeueReusableCell(withIdentifier: "weatherCell", for: indexPath) as! HourlyTableViewCell
//Cell Configure:
cell.textLabel!.font = UIFont.systemFont(ofSize: 10)
return cell
}
}

Answer 1

Where is the code for the VC1 ? Without the code for VC 1 it is hard to give an answer. However i'll try to answer as this might be the scenario.
So basically what you are trying to do is make a network call from the VC2 and whatever the response it should be updated in VC1 which is already active somewhere else. Here you just have to set the delegate of the NetworkManger to the VC1 instance. So you have to get the instance of VC1 in VC2.
var netWorkManager = NetworkManager()
//Get this instance in your code
var vc1: UIViewController!
override func viewDidLoad() {
super.viewDidLoad()
// Here you will be setting the delegate
// to VC1 where you will be having the delegate methods
netWorkManager.delegate = vc1
cityTextField.delegate = self
}
While this method works I would not recommend using the network manager in such a way. Try to use completion handlers instead of delegates to get the data and then pass that values between the view controllers.
Edited:
Pass completion like this in the Network Manager performRequest function.
func performRequest(urlString: String, completion: #escaping (Bool, String?, Error?) -> Void) {
guard let url = URL(string: urlString) else {
completion(false, nil, NSError(domain: "URLString is not a valid URL", code: 100, userInfo: nil))
return
}
let session = URLSession(configuration: .default)
let task = session.dataTask(with: url) { (data, respone, error) in
guard let safeData = data, let weather = self.parseJSON(weatherData: safeData) else {
print("Empty data or JSON parse error")
completion(false, nil, error)
}
print("Im not nil")
completion(true, weather, nil)
}
task.resume()
}
And call the api request in the VC2.
#IBAction func updateWeatherByCityTapped(_ sender: UIButton) {
//Calling the api request. Pass your url string here
self. netWorkManager.performRequest(urlString: "") { (success, weather, error) in
guard success else {
print(error as Any)
return
}
// Here you have got the weather data.
// Don't know what is weather model. so simply passing the weather string.
self.delegate.didUpdateWeather(weather: weather)
//Dismiss the VC:
dismiss(animated: true, completion: nil)
}
}
Here adopt the NetworkManagerDelegate to VC1 and before presenting the VC2 set the delegate to VC1. Or if you are not presenting the VC2 from VC1 then use UserNotifications to send the weather data to the VC1.

Answer 2

This line of code var netWorkManager = NetworkManager() creates a new instance of network manager each time it is invoked.
In your case, the network manager in VC1 will not get called when the network manager you created in VC2 receives a network response. They are two separate entities.
There a few things you can think about:
If I understand your scenario correctly, your VC2 is used to get a city name from the user. Does VC2 really need to make a network call? You could restrict VC2 to only fetch the city name.
Make the networkManager a singleton. You can then call it from multiple places in your code. The networkManger can have method to 'fetch' and it can take in a completionHandler (as #Raja Vijaya kumar) had suggested.