Exercise 1: QuoteFetching Protocol & a Refactored QuoteHeaderView — Possible Solution
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protocol QuoteFetching {
    func fetchQuote() async throws -> Quote
}

struct QuoteService: QuoteFetching {
    func fetchQuote() async throws -> Quote {
        let url = URL(string: "https://api.example.com/quote/today")!
        let (data, response) = try await URLSession.shared.data(from: url)
        guard let httpResponse = response as? HTTPURLResponse,
              httpResponse.statusCode == 200 else {
            throw URLError(.badServerResponse)
        }
        return try JSONDecoder().decode(Quote.self, from: data)
    }
}

struct QuoteHeaderView: View {
    let quoteFetcher: QuoteFetching
    @State private var quote: Quote?

    var body: some View {
        Group {
            if let quote {
                VStack(alignment: .leading, spacing: 4) {
                    Text(quote.text).italic()
                    Text("— \(quote.author)").font(.caption)
                }
            } else {
                ProgressView()
            }
        }
        .task {
            quote = try? await quoteFetcher.fetchQuote()
        }
    }
}

HOW IT WORKS: QuoteFetching declares exactly one real method,
fetchQuote(), matching Fundamentals' own free-standing fetchQuote()
function's signature. QuoteService wraps that same real
URLSession/JSONDecoder logic inside a struct conforming to
QuoteFetching, rather than leaving it as a standalone free function -
this is what makes it substitutable, following the chapter's own
"depend on a protocol, not a concrete implementation" principle.

QuoteHeaderView gains a new real let quoteFetcher: QuoteFetching
property, supplied through its own initializer rather than calling a
hardcoded fetchQuote() function directly inside .task {}. This is
initializer injection, exactly as the chapter's own TaskListViewModel
example demonstrated, applied here to a View instead of a ViewModel.

ANSWER: A QuoteFetching protocol with one fetchQuote() method, a real
QuoteService struct implementing it with the original network logic,
and a refactored QuoteHeaderView receiving its quoteFetcher via
initializer injection rather than calling a hardcoded function
directly, correctly applies this chapter's own dependency-injection
pattern to Fundamentals' own capstone code.

WHY THIS WORKS AS AN ANSWER
------------------------------
This correctly extracts the real networking logic behind a protocol
and refactors the View to receive it via initializer injection,
exactly mirroring the chapter's own TaskListViewModel refactor pattern.