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Project 9 - Day 46 Solution

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Solved Day 46, but with some doubts, posting my solution here and looking to see if I can get some answers/improvement suggestions. In particular, I have a doubt about the last part.

This is what I implemented so far based on the challenge questions

  1. Change project 7 (iExpense) so that it uses NavigationLink for adding new expenses rather than a sheet. (Tip: The dismiss() code works great here, but you might want to add the navigationBarBackButtonHidden() modifier so they have to explicitly choose Cancel.)

  2. Try changing project 7 so that it lets users edit their issue name in the navigation title rather than a separate textfield. Which option do you prefer?

struct ExpensesChallengeView: View {
    @State private var expenses = Expenses()

    var body: some View {
        VStack {
            NavigationStack {
                List {
                   // Display expenses code, code removed for easier reading
                }
                .navigationTitle("iExpense")
                .toolbar {
                    NavigationLink(destination: AddViewChalllengeView(expenses: expenses)) {
                        Image(systemName: "plus")
                    }
                }
            } 
        }
    }

AddView

struct AddViewChalllengeView: View {
    @State private var name = "New Expense"
    @State private var type = "Personal"
    @State private var amount = 0.0

    @Environment(\.dismiss) var dismiss

    var expenses: Expenses

    let types = ["Business", "Personal"]

    var body: some View {
        NavigationStack {
            Form {      
                Picker("Type", selection: $type) {
                    ForEach(types, id: \.self) {
                        Text($0)
                    }
                }

                TextField("Amount", value: $amount, format: .currency(code: Locale.current.currency?.identifier ?? "USD"))
                    .keyboardType(.decimalPad)

            }
            .navigationTitle($name)
            .navigationBarTitleDisplayMode(.inline)
            .toolbar {
                ToolbarItem(placement: .confirmationAction) {
                    Button("Save") {
                        let item = ExpenseItem(name: name, type: type, amount: amount)
                        expenses.items.append(item)
                        dismiss()
                    }
                }

                ToolbarItem(placement: .cancellationAction) {
                    Button("Cancel") {
                        dismiss()
                    }
                }
            }
        }
        .navigationBarBackButtonHidden()
    }

}

Return to project 8 (Moonshot), and upgrade it to use NavigationLink(value:). This means adding Hashable conformance, and thinking carefully how to use navigationDestination().

This is the part i'm confused, I used NavigationLink(value:) in my grid view and had to conform Mission to Hashable, but in doing that, my Mission Struct had a 'does not conform to equatable' error and thus had to make the Mission struct conform to equatable by implementing a custom == function. Why is this the case? This happens after I change MoonshotGridView (shown below) to use NavigationLink(value:) and I just can't see where it's performing an equality comparison.

struct MoonshotGridView: View {
    let astronauts: [String: Astronaut]    
    let missions: [Mission] 
    let columns = [GridItem(.adaptive(minimum: 150))]
    var body: some View {
        ScrollView {
            LazyVGrid(columns: columns) {
                ForEach(missions) { mission in
                    NavigationLink(value: mission) {
                        VStack {
                            Image(mission.image)
                                .resizable()
                                .scaledToFit()
                                .frame(width: 100, height : 100)
                                .padding()

                            VStack {
                                Text(mission.displayName)
                                    .font(.headline)
                                    .foregroundStyle(.white)

                                Text(mission.formattedDate)
                                    .font(.caption)
                                    .foregroundStyle(.gray)
                            }
                            .padding(.vertical)
                            .frame(maxWidth: .infinity)
                            .background(.lightBackground)
                        }
                        .clipShape(.rect(cornerRadius: 10))
                        .overlay(RoundedRectangle(cornerRadius:  10)
                            .stroke(.lightBackground)
                        )
                    }
                    .navigationDestination(for: Mission.self) { mission in
                        MissionView(mission: mission, astronauts: astronauts)
                    }
                } 

            }

            .padding([.horizontal, .bottom])
            .background(.darkBackground)
        }
    }
}

import Foundation

struct Mission: Hashable, Codable, Identifiable, Equatable {

    static func == (lhs: Mission, rhs: Mission) -> Bool {
        return lhs.id == rhs.id
            && lhs.launchDate == rhs.launchDate
            && lhs.crew == rhs.crew
            && lhs.description == rhs.description
    }

    struct CrewRole: Codable, Equatable, Hashable {
        let name: String
        let role: String
    }

    let id: Int
    let launchDate: Date?
    let crew: [CrewRole]
    let description: String

    var displayName: String {
        "Apollo \(id)"
    }

    var image: String {
        "apollo\(id)"
    }

    var formattedDate: String {
        launchDate?.formatted(date: .abbreviated, time: .omitted) ?? "N/A"
    }

}

2      

I tried to reproduce your issue and was unable.

I simply implemented Hashable on my Mission struct and it did not require the Equatable.

Most likely some configuration issue. Check your iOS version, and restart XCode

2      

Hi swiftasroy

Hashable requires ALL elements to conform to Hashable.

struct Mission: Codable, Hashable, Identifiable {
    struct CrewRole: Codable {
        let name: String
        let role: String
    }

    let id: Int
    let launchDate: Date?
    let crew: [CrewRole] // <- CrewRole is not `Hashable`
    let description: String

    // Rest of your code
}

You will get this Type 'Mission' does not conform to protocol 'Equatable' is one of those helpful/unhelpful errors. By making CrewRole also Hashable the error should go away.

struct Mission: Codable, Hashable, Identifiable {
    struct CrewRole: Codable, Hashable {
        let name: String
        let role: String
    }

    let id: Int
    let launchDate: Date?
    let crew: [CrewRole]
    let description: String

    // Rest of your code
}

3      

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