🔒 Let's insert a new feature into the navigation stack. We'll take things step-by-step, employing an enum to hold multiple features in a single package, and making small changes to how we use our existing APIs before sketching out all-new tools dedicated to stack navigation.

🔒 We enhance our navigation stack with a bit more complexity by adding the ability to drill down multiple layers in multiple ways: using the new navigation link API, and programmatically. We also prepare a new feature to add to the stack.

🔒 It's finally time to tackle navigation stacks in the Composable Architecture! They are a

powerful, new tool in SwiftUI and stray a bit from all the other forms of tree-based

navigation we've explored. Let's compare the two styles and see what it takes to integrate

stacks into the library's navigation tools.

🔒 We take a detour to learn about the stack, the heap, copy-on-write, and how we can use this knowledge to further improve our navigation tools by introducing of a property wrapper.

🔒 We now support many different forms of navigation in the Composable Architecture, but if used naively, they open us up to invalid states, like being navigated to several screens at a time. We’ll correct this with the help of Swift's enums.

🔒 While we just tackled drill-down navigation, sadly the API we used was deprecated in iOS 16. Let's get things working with the new `navigationDestination` view modifier, and see what testing in the Composable Architecture has to say about navigation.

🔒 We have a single navigation API powering alerts, dialogs, sheets, popovers, and full screen covers, but what about the prototypical form of navigation, the one that everyone thinks of when they hear "navigation"? It's time to tackle links.

🔒 Let's prepare to delete a *lot* of code. The navigation APIs we've built so far to drive alerts, dialogs, and sheets all have more or less the same shape. We can unify them all in a single package that can also be applied to popovers, fullscreen covers, and more!

🔒 We add superpowers to the navigation tools of the [Composable Architecture][tca-gh], including

automatically cancelling a child feature's effects upon dismissal, and even letting child

features dismiss themselves! Plus, we look at how "non-exhaustive" testing simplifies

navigation-based tests.

[tca-gh]: http://github.com/pointfreeco/swift-composable-architecture

🔒 We tackle a more complex form of navigation: sheets! We'll start with the tools the Composable

Architecture ships today before greatly simplifying them, taking inspiration from the tools we

built for alerts and dialogs.