Set a default back button on a ViewController - ios

Question

short: I don´t understand how to programmatically add the default back button.
long: I have been asked to write an iOS app, without any previous experience I decided
to follow the advices and code given by Nicola Zaghini.
In the code given along with the article, I really don´t understand
where does the back button come from.
The app has three screens
one to choose a city (folder WeatherLocation)
one that displays all
cities that have been already choosen (folder WeatherList)
one that
displays the weather for a city clicked in the list (folder
WeatherDetail)
There is + button for WeatherLocation:
This button is added in the code but I can not find where
and how is coded the back button in WeatherDetails (see above), and how is coded the action to do when one click the back button.
I search the web and found how to set a button in the NavigationBar:
let leftBarButtonItem: UIBarButtonItem = {
let barButtonItem = UIBarButtonItem(title: "Left Item", style: .plain, target: self, action: nil)
barButtonItem.tintColor = UIColor.red
return barButtonItem
}()
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
self.navigationItem.leftBarButtonItem = leftBarButtonItem
}
I also found that there is a backBarButtonItem
but I could not find how to properly use this property.
Moreover in the code of Nicola Zaghini there is nothing like backBarButtonItem to enable the
back button, neither in the xib and storyboard.
Can someone give me some hints about on how to set the back button ?

Answer 1

Thanks a lot!!
In the code of Nicola Zaghini the secret to have a default back button resides (for example) in the function navigateToWeatherDetail in the class WeatherListDefaultRouter where the new ViewController is pushed on a NavigationController:
func navigateToWeatherDetail(withLocation location: Location) {
if let weatherDetailVC = self.weatherDetailBuilder()?.buildWeatherDetailModule(withLocation: location) {
self.viewController?.navigationController?.pushViewController(weatherDetailVC, animated: true)
}
}