Swift : Delegate is nil - ios

Question

I've tried to build a delegate design pattern. I have a simple delegate in WeatherManager , but it's always nil.
I've tried to add weatherManager.delegate = self in override func viewDidLoad() of WeatherViewController.
However, I have another Protocol and delegate, which works fine.
I'm using the API to obtain geographic coordinates from city names, and the URL of the API to get information about the weather is created and executed.
WeatherManager
import Foundation
// delegate design parttern
protocol WeatherManagerDelegate:AnyObject {
func didUpdateWeather(inputWeatherModel: WeatherModel)
}
class WeatherManager {
// delegate
weak var delegate: WeatherManagerDelegate?
// fetchCoordinate
func fetchWeather(urlString: String) {
performRequest(inputURLString: urlString)
}
// performRequest
func performRequest(inputURLString: String) {
// 1. Create URL
if let url = URL(string: inputURLString) {
// 2. Create URLSession
let session = URLSession(configuration: .default)
// 3. Give the URLSession a task
let task = session.dataTask(with: url) { (data, response, error) in
if error != nil {
print(error!)
return
}
if let safeData = data {
if let weather = self.parseJSON(JSONobject: safeData) {
// ---------------- problem here -------------------
self.delegate?.didUpdateWeather(inputWeatherModel: weather)
}
}
}
// 4. Start the task
task.resume()
}
}
// parse JSON object
func parseJSON(JSONobject: Data) -> WeatherModel? {
let decoder = JSONDecoder()
do {
let decodedData = try decoder.decode(WeatherData.self, from: JSONobject)
let id = decodedData.weather[0].id
let temp = decodedData.main.temp
let name = decodedData.name
let weather = WeatherModel(conditionId: id, cityName: name, temperature: temp)
return weather
} catch {
print(error)
return nil
}
}
}
WeatherModel
import Foundation
struct WeatherModel {
let conditionId: Int
let cityName: String
let temperature: Double
var temperatureString: String {
return String(format: "%.1f", temperature)
}
var conditionName: String {
switch conditionId {
case 200...232:
return "cloud.bolt"
case 300...321:
return "cloud.drizzle"
case 500...531:
return "cloud.rain"
case 600...622:
return "cloud.snow"
case 701...781:
return "cloud.fog"
case 800:
return "sun.max"
case 801...804:
return "cloud.bolt"
default:
return "cloud"
}
}
}
WeatherViewController
import UIKit
class WeatherViewController: UIViewController, UITextFieldDelegate, WeatherManagerDelegate {
#IBOutlet weak var conditionImageView: UIImageView!
#IBOutlet weak var temperatureLabel: UILabel!
#IBOutlet weak var searchTextField: UITextField!
#IBOutlet weak var cityLabel: UILabel!
let weatherManager = WeatherManager()
var coordinateManager = CoordinateManager()
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
searchTextField.delegate = self
searchTextField.keyboardType = .asciiCapable
weatherManager.delegate = self
}
#IBAction func searchPressed(_ sender: UIButton) {
searchTextField.endEditing(true)
}
func textFieldShouldReturn(_ textField: UITextField) -> Bool {
searchTextField.endEditing(true)
return true
}
func textFieldShouldEndEditing(_ textField: UITextField) -> Bool {
if textField.text != "" {
return true
} else {
textField.placeholder = "Type Something"
return false
}
}
func textFieldDidEndEditing(_ textField: UITextField) {
if let city = searchTextField.text {
coordinateManager.fetchCoordinate(cityName: city)
}
searchTextField.text = ""
}
func didUpdateWeather(inputWeatherModel: WeatherModel) {
print(inputWeatherModel.temperature)
}
}
CoordinateManager
import Foundation
struct CoordinateManager {
// WeatherManager
let weathetManager = WeatherManager()
// geographical coordinates(lat, lon)　地理座標
let coordinateURL = "https://api.openweathermap.org/geo/1.0/direct?limit=1&appid=c8e60c6317c653a1789294c00f54ae19"
// fetchCoordinate
func fetchCoordinate(cityName: String) {
let urlString = "\(coordinateURL)&q=\(cityName)"
performRequest(inputURLString: urlString)
}
// transformURLString
func transformURLString(_ string: String) -> URLComponents? {
guard let urlPath = string.components(separatedBy: "?").first else {
return nil
}
var components = URLComponents(string: urlPath)
if let queryString = string.components(separatedBy: "?").last {
components?.queryItems = []
let queryItems = queryString.components(separatedBy: "&")
for queryItem in queryItems {
guard let itemName = queryItem.components(separatedBy: "=").first,
let itemValue = queryItem.components(separatedBy: "=").last else {
continue
}
components?.queryItems?.append(URLQueryItem(name: itemName, value: itemValue))
}
}
return components!
}
// performRequest
func performRequest(inputURLString: String) {
// 1. Create URL
let components = transformURLString(inputURLString)
if let url = components?.url {
// 2. Create URLSession
let session = URLSession(configuration: .default)
// 3. Give the URLSession a task
let task = session.dataTask(with: url) {(data, response, error) in
if error != nil {
print(error!)
return
}
if let safeData = data {
self.parseJSON(JSONobject: safeData)
}
}
// 4. Start the task
task.resume()
}
}
// parseJSON
func parseJSON(JSONobject: Data) {
let decoder = JSONDecoder()
do {
let decodedData = try decoder.decode([CoordinateData].self, from: JSONobject)
let name = decodedData[0].name
let lat = decodedData[0].lat
let lon = decodedData[0].lon
let coordinateModel = CoordinateModel(name: name, lat: lat, lon: lon)
let weatherURL = coordinateModel.urlString
// ------- WeatherManager fetchWeather ---------
weathetManager.fetchWeather(urlString: weatherURL)
} catch {
print(error)
}
}
}
CoordinateModel
import Foundation
struct CoordinateModel {
let name: String
let lat: Double
let lon: Double
// wheather　地理座標を元に検索した天気の情報
let weatherstr = "https://api.openweathermap.org/data/2.5/weather?"
let str = "units=metric&appid=c8e60c6317c653a1789294c00f54ae19#"
// computedproperty
var urlString: String {
return "\(weatherstr)&lat=\(lat)&lon=\(lon)&\(str)"
}
}

Answer 1

You create a weatherManager in the WeatherViewController , and in the viewDidLoad method you set the WeatherViewController as a delegate to the weatherManager instance you created here. In the CoordinateManager class, you create a new weatherManager, and don't set a delegate for it.
2 solutions, use what is most convenient for you:
Create an initializer for the CoordinateManager, to pass it the WeatherManager that you have created and that you are listening to
// CoordinateManager class
let weatherManager: WeatherManager
init(weatherManager: WeatherManager) {
self.weatherManager = weatherManager
}
// WeatherViewController class
let weatherManager = WeatherManager()
var coordinateManager = CoordinateManager(weatherManager: weatherManager)
You can directly set WeatherViewController as a delegate to the desired weatherManager instance.
// WeatherViewController class
override func viewDidLoad() {
super.viewDidLoad()
searchTextField.delegate = self
searchTextField.keyboardType = .asciiCapable
// Instead weatherManager.delegate = self
coordinateManager.weatherManager.delegate = self
}