MultiNav

A SwiftUI navigation scheme (iOS 17 only), providing an easy-to-use interface for presenting Views, and managing ViewModels.

Features

• The Navigation stack is managed using push(), pop(), popToRoot(), and jumpTo(), from either the View, or ViewModel.
• All Views belonging to a given Navigation stack are defined in one central location (NavigationScreenDefinition enum).
• Simplified, standardized modal presentation.
• All ViewModels are owned, and their lifetimes managed, by a central NavigationCoordinator (and not by other Views, or ViewModels).
• A single instance of a ViewModel can be shared between multiple Views.

Limitations

• The NavigationCoordinator supports no more than one ViewModel per View.
• Each View/ViewModel combo must be uniquely identifiable by one or more Hashable elements.

Modals

A parent View can easily present a child View as a sheet, or a fullScreenCover. Alerts can be easily presented, and managed as well. In order to do this:

1. The parent ViewModel must inherit from ModalPresenter.
2. The parent View must use the .modalPresenting() view modifier.
3. The presented (child) View must be defined in the same NavigationScreenDefinition enum as its parent View.
4. ModalPresenter.presentModal(), and ModalPresenter.presentAlert() can be used from either the View, or the ViewModel.

Technical Notes

NavigationRootView

Represents the root of a navigation stack. An app can contain one or more of these. Each one requires its own instance of NavigationCoordinator, which in turn requires a NavigationScreenDefinition enum.

NavigationScreenDefinition

Protocol. Typically implemented by an enum, with associated values. Each instance (enum case) corresponds to a screen in the app.

NavigationScreenDefinition.screenView()

This func must be implemented to return the actual View corresponding to each NavigationScreenDefinition instance. This may also involve creating a corresponding ViewModel.

NavigationCoordinator

The relevant instance of this is automatically available (via Environment) to every View under a given navigation stack (NavigationRootView). It can also be provided to any ViewModel, upon creation.

NavigationCoordinator.push(), pop(), popToRoot()

Can be called from View, or ViewModel, as needed.

NavigationCoordinator.jumpTo()

Replaces the entire navigation stack with another one, in a single call.

NavigationCoordinator.observable(for: default:)

Call this func to create and register a ViewModel, or simply return it, if it already exists. (ViewModels are automatically released when their corresponding Views are dismissed). Typically used within NavigationScreenDefinition.screenView(), during View creation.

ModalPresentor

Make this the superclass of a ViewModel in order to facilitate modal presentation of Views from either it, or its corresponding View. This also facilitates flexible presentation and handling of alerts.

• The corresponding View must apply the .modalPresenting() view modifier (wherever the .sheet(), or .fullScreenCover() modifiers would be used).
• A single ModalPresentor ViewModel cannot be shared across more than one View needing to present child Views modally.

ModalPresentor.presentModal(_: isFullScreen:)

Can be called from View, or ViewModel, as needed.

ModalPresentor.presentAlert()

Can be called from View, or ViewModel, as needed.

ModalPresentor.handleAlertButton(id:)

Override this func in a ViewModel. It is called whenever an alert button is tapped.