Final assessment

Twelve questions across the whole course. Score 70% or more to pass and unlock your certificate. You can retake it as often as you like.

Finish every lesson to earn the certificate — you can take the assessment any time.

expenses is an empty array. What is label?

Swift

let label = expenses.first?.title.uppercased() ?? "NONE"

It crashes, because the array is empty.
nil
An empty string.
"NONE"

Pocket Budget needs a sort-order setting with exactly three choices (newest, oldest, largest) shown in a picker and saved to disk. Which type fits best?

enum SortOrder: String, CaseIterable { case newest, oldest, largest }
let sortOrder: String
struct SortOrder { var isNewest: Bool; var isLargest: Bool }
class SortOrder with three subclasses.

Why does the add-expense form keep title, amount and category in its own @State properties instead of writing to the store on every keystroke?

Because @Observable stores can’t be edited from forms.
Because TextField only works with @State.
Because the store can only accept complete Expense values.
So the form is a draft: Cancel discards it without touching saved data.

You add case gifts to Category. The project has three switch statements over Category, yet the build passes with no errors. What’s the most likely explanation?

Swift doesn’t check switch exhaustiveness for enums with raw values.
New enum cases are only checked when you run the app.
Those switches use default:, which silently absorbs the new case.
Xcode only checks switches in files you have open.

Several tasks fetch rates in parallel and must all update one shared cache. Which declaration keeps the cache free of data races?

actor RateCache { private var rates: [String: Decimal] = [:] } with methods to read and save.
final class RateCache { var rates: [String: Decimal] = [:] }
struct RateCache { var rates: [String: Decimal] } passed to each task.
A global var rates: [String: Decimal].

The JSON contains "total_spent": 12.5 and your struct has let totalSpent: Decimal. Decoding throws keyNotFound. What’s the cleanest fix?

Rename the property to total_spent.
Change the type to Double.
Make the property optional.
Set decoder.keyDecodingStrategy = .convertFromSnakeCase.

Users want to pull down on the rates list to refresh it. Which modifier adds that?

.task { await model.load() }
.refreshable { await model.load() }
.onTapGesture { Task { await model.load() } }
.sheet(isPresented:)

In which situation is try? a good choice?

Deleting a temporary export file that may already be gone, where failure changes nothing.
Saving the user’s new expense.
Decoding the exchange-rate response.
Recording an expense against a budget limit.

Which declaration shows saved expenses newest first and updates on its own when another screen inserts one?

@State private var expenses: [Expense] = []
let expenses = try? context.fetch(FetchDescriptor<Expense>())
@Environment(\.modelContext) private var expenses
@Query(sort: \Expense.date, order: .reverse) private var expenses: [Expense]

What does some View in var body: some View promise?

That body can return a different view type each time it’s called.
That the view is a class.
That body returns one specific type conforming to View, which the compiler knows but you don’t have to write.
That the view will be rendered on a background thread.

Uploading a new build to App Store Connect fails because that build number was already used for this version. What do you do?

Increase the Build number in the target settings, archive again and upload.
Delete the earlier build from TestFlight and retry.
Change the bundle identifier.
Wait 90 days for the old build to expire.

Does this compile?

Swift

@Observable
final class Settings {
    var limit: Decimal = 100
}
let settings = Settings()
settings.limit = 200

No, because settings is a let constant.
No, because @Observable properties are read-only.
Yes, but the change is lost because settings was copied.
Yes; the reference is constant, but the object’s var property can still change.

12 questions unanswered