Inherit from EPUBNavigatorViewController?

[domkm]

This looks easy enough with PDFNavigatorViewController and AudioNavigator, because their designated initializers are the recommended initializers. However, for EPUBNavigatorViewController, the recommended initializer is a convenience initializer, which cannot be called from a subclass without first calling the designated initializer. The designated initializer of EPUBNavigatorViewController is rather complicated and appears to not be usable in practice because it doesn't set the view model, which itself is an internal type. I cannot figure out how to inherit from EPUBNavigatorViewController, but I would very much like to so that functionality like highlighting can be implemented without keeping track of a separate view controller that doesn't have navigator functionality. Would it be possible to remove the convenience keyword of the recommended initializer for EPUBNavigatorViewController?

[mickael-menu]

I wouldn't rely on inheritance when it's not explicitly designed for in the toolkit. Inheritance can be tricky and lead to hard-to-find bugs if you override things incorrectly. So it's preferable to use composition over inheritance.

Here's the recommended way to catch events from the responder chain, such as a highlight event:

class ReaderViewController<N: UIViewController & Navigator>: UIViewController {
    let navigator: N

    init(navigator: N) {
        self.navigator = navigator
        super.init(nibName: nil, bundle: nil)
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()

        addChild(navigator)
        navigator.view.frame = view.bounds
        navigator.view.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        view.addSubview(navigator.view)
        navigator.didMove(toParent: self)
    }

    @objc func highlightSelection() {
    }
}

var editingActions = EditingAction.defaultActions
editingActions.append(EditingAction(
    title: "Highlight",
    action: #selector(ReaderViewController.highlightSelection)
)

let vc = ReaderViewController(navigator: EPUBNavigatorViewController(
    publication: publication,
    initialLocation: locator,
    config: EPUBNavigatorViewController.Configuration(
        editingActions: editingActions
    ),
))

I know this may not be the answer you expected, but I believe it's for the good of your codebase. Note that with this technique you will be able to reuse the highlighting code for all the navigators supporting it (PDF, at some point) as you don't subclass individual navigator classes.

[domkm]

Okay, will do. Thank you for the explanation and example code.