Why self delegate is nil? - ios

Question

I want to make a weather application by adding a city name with openweathermap api. But I could not send the city I added in AddCityViewController back to HomeViewController. Because, self?.delegate is nil, in AddCityViewController.swift
#objc private func didTapSaveButton() {
print("clicked save button")
if let city = cityTextfield.text {
let weatherURL = URL(string: "https://api.openweathermap.org/data/2.5/weather?q=\(city)&APPID=b4251cb51691654da529bccf471596bc&units=imperial")!
let weatherResource = Resource<WeatherViewModel>(url: weatherURL) { data in
let weatherVM = try? JSONDecoder().decode(WeatherViewModel.self, from: data)
return weatherVM
}
Webservice().load(resource: weatherResource) { [weak self] result in
if let weatherVM = result {
if let delegate = self?.delegate {
delegate.addWeatherDidSave(vm: weatherVM)
self?.dismiss(animated: true, completion: nil)
}
}
}
}
}
When I debug the prepare function in HomeViewController.swift was not getting called.
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
guard let nav = segue.destination as? UINavigationController else {
fatalError("NavigationController not found")
}
guard let addWeatherCityVC = nav.viewControllers.first as? AddCityViewController else {
fatalError("AddWeatherCityController not found")
}
addWeatherCityVC.delegate = self
}
What I want is, I want to pass the city name back to HomeViewController when user press the save button.
extension HomeViewController: AddWeatherDelegate {
func addWeatherDidSave(vm: WeatherViewModel) {
print(vm.name)
}
}
Source code in GitHub

Answer 1

You are not using segue for navigation, so the prepareForSegue method won't get triggered. In your code, you are manually initialising an instance of AddCityViewController and presenting it. So to fix the issue, you have to set delegate to that instance.
#objc private func didTapAddButton() {
let vc = AddCityViewController()
vc.title = "Add City"
vc.delegate = self
let nav = UINavigationController(rootViewController: vc)
nav.modalPresentationStyle = .fullScreen
present(nav, animated: true)
}
Or else you can use segue for navigation.