I'm reviewing Moonshot as part of 100 days of SwiftUI and have a bit of trouble connecting the dots on a few things. I'm hoping someone can explain these few things to me:

Question 1: In ContentView, not fully understanding how we are defining missions and astronaut, referring this code:

let astronauts: [String: Astronaut] = Bundle.main.decode("astronauts.json")
let missions: [Mission] = Bundle.main.decode("missions.json")

Question 2: In ContentView, why are we passing in mission: mission, and not missions: missions? Referring this code:

ForEach(missions) { mission in
                        NavigationLink {
                            MissionView(mission: mission, astronauts: astronauts)
                        } label: {
                            VStack {

Question 3: How is it being decided which objects to bring in and what to pass in? I think majority of my questions are me trying to understand how missions and astronaut are being passed in, since in various parts of the code in this project, they have slightly different names/ways they are being passed in?

Question 4: Can someone explain the custom initializer in MissionView, referring to this code:

 init(mission: Mission, astronauts: [String: Astronaut]) {
        self.mission = mission
        self.crew = mission.crew.map { member in
            if let astronaut = astronauts[member.name] {
                return CrewMember(role: member.role, astronaut: astronaut)
            } else {
                fatalError("Missing \(member.name)")
            }
        }
    }

Thank you!

Question 2: ForEach parameter

A new programmer asks:

Why are we passing in mission: mission, and not missions: missions? Referring this code:

ForEach(missions) { mission in
NavigationLink {
MissionView(mission: mission, astronauts: astronauts)
} label: {
VStack {   //.... snip! .... 

I like to think of ForEach as a view factory!
See -> View Factory
or See -> View Factory
or See -> View Factory

So, ask yourself: In the code snip above what is the ForEach view factory trying to make?

It appears you're trying to build several NavigationLink views, one NavigationLink for each of the moon missions. Convince yourself this is what you are building with the ForEach factory.

Now that you understand that the ForEach builds separate, independent views, your next questions is: What are the raw materials the ForEach factory needs to build a NavigationLink view?

Raw Materials

1. The ForEach view factory needs a label. This label probably has the title of the mission, maybe a small graphic. It's something that your user will recognize and eventually tap on.
2. Because you are building a navigation destination, the ForEach view factory needs to know what view to show when the user taps the NavigationLink.

In the Moonshot application, when you tap a mission label, you'll want to send the user to a fully defined MissionView(). So what does SwiftUI need to create a single MissionView() view? It needs one, and only one, mission object.

Clarify Intent

I think it confuses new developers when the parameter labels match the incoming variable labels. I am often overruled in this opinion. But here's a great example of how this can be confusing.

// Confusing?
MissionView(mission: mission, astronauts: astronauts)

The MissionView view needs a single mission, and an array of astronauts. The programmer used the same name for the paramater and variable.

// Less confusing?
// This builds ONE and ONLY ONE mission view.
MissionView(showing: mission, withAstronauts: allApolloAstronauts)

This is more verbose, but maybe we can agree this is somewhat more understandable?