Day 53, 54, 55, 56 of #100DaysOfSwiftUI

Start 100DaysOfSwiftUI from 2020.Mar.18th.

Day 53, 54, 55, 56: Project 11, part one/two/three/four
done with 5 hours

New findings: followings are new findings

AnyView

this should be useful to show variable views which depends on the condition.

Really fun !

ContentView.swift

struct ContentView: View {
    @Environment(\.managedObjectContext) var moc
    @FetchRequest(entity: Book.entity(), sortDescriptors: [
        NSSortDescriptor(keyPath: \Book.title, ascending: true),
        NSSortDescriptor(keyPath: \Book.author, ascending: true)
    ]) var books: FetchedResults

    @State private var showingAddScreen = false

    var body: some View {
        NavigationView {
            List {
                ForEach(books, id: \.self) { book in
                    NavigationLink(destination: DetailView(book: book)) {
                        EmojiRatingView(rating: book.rating)
                            .font(.largeTitle)

                        VStack(alignment: .leading) {
                            Text(book.title ?? "Unknown Title")
                                .font(.headline)
                                .foregroundColor(book.rating == 1 ? Color.red : .black)
                            Text(book.author ?? "Unknown Author")
                                .foregroundColor(.secondary)
                        }
                    }
                }
            .onDelete(perform: deleteBooks)
            }
            .navigationBarTitle("Bookworm")
            .navigationBarItems(leading: EditButton(),
                trailing: Button(action: {
                self.showingAddScreen.toggle()
            }, label: {
                Image(systemName: "plus")
            }))
                .sheet(isPresented: $showingAddScreen, content: {
                    AddBookView().environment(\.managedObjectContext, self.moc)
                })
        }
    }
    
    func deleteBooks(at offsets:IndexSet) {
        for offset in offsets {
            let book = books[offset]
            moc.delete(book)
        }
        try? moc.save()
    }
    
}

AddBookView.swift

struct AddBookView: View {
    @Environment(\.presentationMode) var presentationMode
    @Environment(\.managedObjectContext) var moc
    @State private var title = ""
    @State private var author = ""
    @State private var rating = 3
    @State private var genre = ""
    @State private var review = ""
    
    let genres = ["Fantasy", "Horror", "Kids", "Mystery", "Poetry", "Romance", "Thriller"]
    
    var body: some View {
        NavigationView {
            Form {
                Section {
                    TextField("Name of book", text: $title)
                    TextField("Author's name", text: $author)
                    
                    Picker("Genre", selection: $genre) {
                        ForEach(genres, id:\.self) {
                            Text($0)
                        }
                    }
                }
                Section {
                    RatingView(rating: $rating)
                    TextField("Write a review", text: $review)
                }
                Section {
                    Button("Save") {
                        let newBook = Book(context: self.moc)
                        newBook.title = self.title
                        newBook.author = self.author
                        newBook.rating = Int16(self.rating)
                        newBook.genre = self.genre
                        newBook.review = self.review
                        newBook.date = Date()
                        try? self.moc.save()
                        self.presentationMode.wrappedValue.dismiss()
                    }
                }
            .disabled(genre == "")
            }
        .navigationBarTitle("Add Book")
        }
    }
}

RatingView.swift

struct RatingView: View {
    @Binding var rating: Int

    var label = ""

    var maximumRating = 5

    var offImage: Image?
    var onImage = Image(systemName: "star.fill")

    var offColor = Color.gray
    var onColor = Color.yellow
    
    var body: some View {
        HStack {
            if label.isEmpty == false {
                Text(label)
            }

            ForEach(1.. self.rating ? self.offColor : self.onColor)
                    .onTapGesture {
                        self.rating = number
                    }
            }
        }
    }
    
    func image(for number: Int) -> Image {
        if number > rating {
            return offImage ?? onImage
        } else {
            return onImage
        }
    }
}

EmpjoRatingView.swift

struct EmojiRatingView: View {
    let rating: Int16
    
    var body: some View {
        switch rating {
        case 1:
            return Text("①")
        case 2:
            return Text("②")
        case 3:
            return Text("③")
        case 4:
            return Text("④")
        default:
            return Text("⑤")
        }
    }
}

DetailView.swift

struct DetailView: View {
    @Environment(\.managedObjectContext) var moc
    @Environment(\.presentationMode) var presentationMode
    @State private var showingDeleteAlert = false
    let book: Book
    var body: some View {
        GeometryReader { geometry in
            VStack {
                ZStack(alignment: .bottomTrailing) {
                    Image(self.book.genre ?? "Fantasy")
                        .frame(maxWidth: geometry.size.width)

                    Text(self.book.genre?.uppercased() ?? "FANTASY")
                        .font(.caption)
                        .fontWeight(.black)
                        .padding(8)
                        .foregroundColor(.white)
                        .background(Color.black.opacity(0.75))
                        .clipShape(Capsule())
                        .offset(x: -5, y: -5)
                }
                Text(self.book.author ?? "Unknown author")
                    .font(.title)
                    .foregroundColor(.secondary)

                Text(self.book.review ?? "No review")
                    .padding()

                RatingView(rating: .constant(Int(self.book.rating)))
                    .font(.largeTitle)

                Spacer()
                Text("Date:  \(self.formattedDate(book: self.book))")
                Spacer()
            }
        }
        .navigationBarTitle(Text(book.title ?? "Unknown Book"), displayMode: .inline)
    .navigationBarItems(trailing: Button(action: {
        self.showingDeleteAlert = true
    }, label: {
        Image(systemName: "trash")
    }))
        .alert(isPresented: $showingDeleteAlert) {
            Alert(title: Text("Delete book"), message: Text("Are you sure?"), primaryButton: .destructive(Text("Delete")) {
                    self.deleteBook()
                }, secondaryButton: .cancel()
            )
        }
    }
    
    func deleteBook() {
        moc.delete(book)

        // uncomment this line if you want to make the deletion permanent
        try? self.moc.save()
        presentationMode.wrappedValue.dismiss()
    }
    
    func formattedDate(book:Book) -> String {
        if let date = book.date {
            let formatter = DateFormatter()
            formatter.dateStyle = .long
            return formatter.string(from: date)
        }
        return "N/A"
    }
    
}