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Moonshot: Wrap up

Paul Hudson    @twostraws   

This app is the most complex one we’ve built so far. Yes, there are multiple views, but we also strayed away from lists and forms and into our own scrolling layouts, using containerRelativeFrame() to get precise sizes to make the most of our space.

But this was also the most complex Swift code we’ve written so far – generics are an incredibly powerful feature, and once you add in constraints you open up a huge range of functionality that lets you save time while also gaining flexibility.

You’re also now starting to see how useful Codable is: its ability to decode a hierarchy of data in one pass is invaluable, which is why it’s central to so many Swift apps.

Review what you learned

Anyone can sit through a tutorial, but it takes actual work to remember what was taught. It’s my job to make sure you take as much from these tutorials as possible, so I’ve prepared a short review to help you check your learning.

Click here to review what you learned in this project.


One of the best ways to learn is to write your own code as often as possible, so here are three ways you should try extending this app to make sure you fully understand what’s going on.

  1. Add the launch date to MissionView, below the mission badge. You might choose to format this differently given that more space is available, but it’s down to you.
  2. Extract one or two pieces of view code into their own new SwiftUI views – the horizontal scroll view in MissionView is a great candidate, but if you followed my styling then you could also move the Rectangle dividers out too.
  3. For a tough challenge, add a toolbar item to ContentView that toggles between showing missions as a grid and as a list.

Hacking with Swift+ subscribers can get a complete video solution for this checkpoint here: Solution to Moonshot. If you don’t already subscribe, you can start a free trial today.

Tip: For that last one, your best bet is to make all your grid code and all your list code two separate views, and switch between them using an if condition in ContentView. You can’t attach SwiftUI modifiers to an if condition, but you can wrap that condition in a Group then attach modifiers to there, like this:

Group {
    if showingGrid {
        GridLayout(astronauts: astronauts, missions: missions)
    } else {
        ListLayout(astronauts: astronauts, missions: missions)
.navigationTitle("My Group")

You might hit some speed bumps trying to style your list, because they have a particular look and feel on iOS by default. Try attaching .listStyle(.plain) to your list, then something like .listRowBackground(Color.darkBackground) to the contents of your list row – that should get you a long way towards your goal.

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