Neil Smith is a subscriber to the Clean Swift list. He recently sent me an email asking about coordinator, protocol, naming, and closure.
After a few exchanges, I thought the discussion would be very beneficial to all of you. So I asked Neil if I could share it. He said yes. So here you have it.
There is a subtle change in the latest template update. The variables viewController, interactor, and presenter are now declared as real optionals using ?. (They were forced unwrapped optionals with ! before.)
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 |
class CreateOrderViewController: CreateOrderDisplayLogic { var interactor: CreateOrderBusinessLogic? } class CreateOrderInteractor: CreateOrderBusinessLogic { var presenter: CreateOrderPresentationLogic? } class CreateOrderPresenter: CreateOrderPresentationLogic { var viewController: CreateOrderDisplayLogic? } |
Why?
There was a situation where it could cause a crash if presenter is deallocated and a method is invoked on it.
This happens when the interactor does some asynchronous work. Before it can finish, the user has navigated away (such as tapping the back button) from the current scene.
This is a very common question. If you follow the MVC pattern, like all the tutorials and Apple sample code, your view controllers conform to a lot of protocols.
UITableViewDataSource, UITableViewDelegate, and UICollectionViewDataSource, UICollectionViewDelegate are the most common ones.
If your UI collects user inputs, you also have UIPickerViewDataSource, UIPickerViewDelegate, and UITextFieldDelegate.
What if you show a map? You can count on having MKMapViewDelegate and CLLocationManagerDelegate.
Almost all apps fetch data from APIs, so you also have some of these: URLSessionDelegate, URLSessionTaskDelegate, URLSessionDataDelegate, URLSessionDownloadDelegate.
I can keep going, but let’s just stop here.
Your view controllers conform to many of these Apple provided protocols, plus any custom protocols you define for your app. Each of these protocols has several delegate methods your view controllers need to implement. It can easily get out of hand.
This is one reason contributing to your massive view controllers. Let’s see how Clean Swift tackles this problem.
Some of you have raised the annoyance of having to declare the same methods in duplicate input and output protocols, in separate files.
I hear ya. You’ll love that they’re now gone in the latest update to the Clean Swift Xcode templates.
Read along to find out why those good, old reasons have become compromises that need to be re-evaluated and ultimately removed.
The configurator in Clean Swift has two functions:
Now that the protocols are no longer duplicated, the first function is not needed anymore. That leaves only the second.
It’s worthwhile to rethink if there’s a better way to set up the VIP cycle.
Among the feedback that I receive are:
configure(viewController:) method is only invoked from UIViewController‘s awakeFromNib() method.Keep reading to find out how each of these has been taken care of in the latest update.