[HasCustomView] Define a custom property for `UIViewController` to use a typed view #swift #ios

HasCustomView.swift

/// The HasCustomView protocol defines a customView property for UIViewControllers to be used in exchange of the regular view property.
/// In order for this to work, you have to provide a custom view to your UIViewController at the loadView() method.
public protocol HasCustomView {
    associatedtype CustomView: UIView
}

extension HasCustomView where Self: UIViewController {
    /// The custom typed view
    public var customView: CustomView {
        guard let customView = view as? CustomView else {
            fatalError("Expected view to be of type \(CustomView.self) but got \(type(of: view)) instead")
        }
        return customView
    }
}