The SwiftUI cookbook for navigation

The SwiftUI cookbook for navigation

The recipe for a great app begins with a clear and robust navigation structure. Join the SwiftUI team in our proverbial coding kitchen and learn how you can cook up a great experience for your app. We'll introduce you to SwiftUI's navigation stack and split view features, show you how you can link to specific areas of your app, and explore how you can quickly and easily restore navigational state.

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import SwiftUI

// Pushable stack
struct PushableStack: View {
    @State private var path: [Recipe] = []
    @StateObject private var dataModel = DataModel()

    var body: some View {
        NavigationStack(path: $path) {
            List(Category.allCases) { category in
                Section(category.localizedName) {
                    ForEach(dataModel.recipes(in: category)) { recipe in
                        NavigationLink(recipe.name, value: recipe)
                    }
                }
            }
            .navigationTitle("Categories")
            .navigationDestination(for: Recipe.self) { recipe in
                RecipeDetail(recipe: recipe)
            }
        }
        .environmentObject(dataModel)
    }
}

// Helpers for code example
struct RecipeDetail: View {
    @EnvironmentObject private var dataModel: DataModel
    var recipe: Recipe

    var body: some View {
        Text("Recipe details go here")
            .navigationTitle(recipe.name)
        ForEach(recipe.related.compactMap { dataModel[$0] }) { related in
            NavigationLink(related.name, value: related)
        }
    }
}

class DataModel: ObservableObject {
    @Published var recipes: [Recipe] = builtInRecipes

    func recipes(in category: Category?) -> [Recipe] {
        recipes
            .filter { $0.category == category }
            .sorted { $0.name < $1.name }
    }

    subscript(recipeId: Recipe.ID) -> Recipe? {
        // A real app would want to maintain an index from identifiers to
        // recipes.
        recipes.first { recipe in
            recipe.id == recipeId
        }
    }
}

enum Category: Int, Hashable, CaseIterable, Identifiable, Codable {
    case dessert
    case pancake
    case salad
    case sandwich

    var id: Int { rawValue }

    var localizedName: LocalizedStringKey {
        switch self {
        case .dessert:
            return "Dessert"
        case .pancake:
            return "Pancake"
        case .salad:
            return "Salad"
        case .sandwich:
            return "Sandwich"
        }
    }
}

struct Recipe: Hashable, Identifiable {
    let id = UUID()
    var name: String
    var category: Category
    var ingredients: [Ingredient]
    var related: [Recipe.ID] = []
    var imageName: String? = nil
}

struct Ingredient: Hashable, Identifiable {
    let id = UUID()
    var description: String

    static func fromLines(_ lines: String) -> [Ingredient] {
        lines.split(separator: "\n", omittingEmptySubsequences: true)
            .map { Ingredient(description: String($0)) }
    }
}

let builtInRecipes: [Recipe] = {
    var recipes = [
        "Apple Pie": Recipe(
            name: "Apple Pie", category: .dessert,
            ingredients: Ingredient.fromLines(applePie)),
        "Baklava": Recipe(
            name: "Baklava", category: .dessert,
            ingredients: []),
        "Bolo de Rolo": Recipe(
            name: "Bolo de rolo", category: .dessert,
            ingredients: []),
        "Chocolate Crackles": Recipe(
            name: "Chocolate crackles", category: .dessert,
            ingredients: []),
        "Crème Brûlée": Recipe(
            name: "Crème brûlée", category: .dessert,
            ingredients: []),
        "Fruit Pie Filling": Recipe(
            name: "Fruit Pie Filling", category: .dessert,
            ingredients: []),
        "Kanom Thong Ek": Recipe(
            name: "Kanom Thong Ek", category: .dessert,
            ingredients: []),
        "Mochi": Recipe(
            name: "Mochi", category: .dessert,
            ingredients: []),
        "Marzipan": Recipe(
            name: "Marzipan", category: .dessert,
            ingredients: []),
        "Pie Crust": Recipe(
            name: "Pie Crust", category: .dessert,
            ingredients: Ingredient.fromLines(pieCrust)),
        "Shortbread Biscuits": Recipe(
            name: "Shortbread Biscuits", category: .dessert,
            ingredients: []),
        "Tiramisu": Recipe(
            name: "Tiramisu", category: .dessert,
            ingredients: []),
        "Crêpe": Recipe(
            name: "Crêpe", category: .pancake, ingredients: []),
        "Jianbing": Recipe(
            name: "Jianbing", category: .pancake, ingredients: []),
        "American": Recipe(
            name: "American", category: .pancake, ingredients: []),
        "Dosa": Recipe(
            name: "Dosa", category: .pancake, ingredients: []),
        "Injera": Recipe(
            name: "Injera", category: .pancake, ingredients: []),
        "Acar": Recipe(
            name: "Acar", category: .salad, ingredients: []),
        "Ambrosia": Recipe(
            name: "Ambrosia", category: .salad, ingredients: []),
        "Bok l'hong": Recipe(
            name: "Bok l'hong", category: .salad, ingredients: []),
        "Caprese": Recipe(
            name: "Caprese", category: .salad, ingredients: []),
        "Ceviche": Recipe(
            name: "Ceviche", category: .salad, ingredients: []),
        "Çoban salatası": Recipe(
            name: "Çoban salatası", category: .salad, ingredients: []),
        "Fiambre": Recipe(
            name: "Fiambre", category: .salad, ingredients: []),
        "Kachumbari": Recipe(
            name: "Kachumbari", category: .salad, ingredients: []),
        "Niçoise": Recipe(
            name: "Niçoise", category: .salad, ingredients: []),
    ]

    recipes["Apple Pie"]!.related = [
        recipes["Pie Crust"]!.id,
        recipes["Fruit Pie Filling"]!.id,
    ]

    recipes["Pie Crust"]!.related = [recipes["Fruit Pie Filling"]!.id]
    recipes["Fruit Pie Filling"]!.related = [recipes["Pie Crust"]!.id]

    return Array(recipes.values)
}()

let applePie = """
    ¾ cup white sugar
    2 tablespoons all-purpose flour
    ½ teaspoon ground cinnamon
    ¼ teaspoon ground nutmeg
    ½ teaspoon lemon zest
    7 cups thinly sliced apples
    2 teaspoons lemon juice
    1 tablespoon butter
    1 recipe pastry for a 9 inch double crust pie
    4 tablespoons milk
    """

let pieCrust = """
    2 ½ cups all purpose flour
    1 Tbsp. powdered sugar
    1 tsp. sea salt
    ½ cup shortening
    ½ cup butter (Cold, Cut Into Small Pieces)
    ⅓ cup cold water (Plus More As Needed)
    """

struct PushableStack_Previews: PreviewProvider {
    static var previews: some View {
        PushableStack()
    }
}

10:40 - Multiple Columns

import SwiftUI

// Multiple columns
struct MultipleColumns: View {
    @State private var selectedCategory: Category?
    @State private var selectedRecipe: Recipe?
    @StateObject private var dataModel = DataModel()

    var body: some View {
        NavigationSplitView {
            List(Category.allCases, selection: $selectedCategory) { category in
                NavigationLink(category.localizedName, value: category)
            }
            .navigationTitle("Categories")
        } content: {
            List(
                dataModel.recipes(in: selectedCategory),
                selection: $selectedRecipe)
            { recipe in
                NavigationLink(recipe.name, value: recipe)
            }
            .navigationTitle(selectedCategory?.localizedName ?? "Recipes")
        } detail: {
            RecipeDetail(recipe: selectedRecipe)
        }
    }
}

// Helpers for code example
struct RecipeDetail: View {
    var recipe: Recipe?

    var body: some View {
        Text("Recipe details go here")
            .navigationTitle(recipe?.name ?? "")
    }
}

class DataModel: ObservableObject {
    @Published var recipes: [Recipe] = builtInRecipes

    func recipes(in category: Category?) -> [Recipe] {
        recipes
            .filter { $0.category == category }
            .sorted { $0.name < $1.name }
    }
}

enum Category: Int, Hashable, CaseIterable, Identifiable, Codable {
    case dessert
    case pancake
    case salad
    case sandwich

    var id: Int { rawValue }

    var localizedName: LocalizedStringKey {
        switch self {
        case .dessert:
            return "Dessert"
        case .pancake:
            return "Pancake"
        case .salad:
            return "Salad"
        case .sandwich:
            return "Sandwich"
        }
    }
}

struct Recipe: Hashable, Identifiable {
    let id = UUID()
    var name: String
    var category: Category
    var ingredients: [Ingredient]
    var related: [Recipe.ID] = []
    var imageName: String? = nil
}

struct Ingredient: Hashable, Identifiable {
    let id = UUID()
    var description: String

    static func fromLines(_ lines: String) -> [Ingredient] {
        lines.split(separator: "\n", omittingEmptySubsequences: true)
            .map { Ingredient(description: String($0)) }
    }
}

let builtInRecipes: [Recipe] = {
    var recipes = [
        "Apple Pie": Recipe(
            name: "Apple Pie", category: .dessert,
            ingredients: Ingredient.fromLines(applePie)),
        "Baklava": Recipe(
            name: "Baklava", category: .dessert,
            ingredients: []),
        "Bolo de Rolo": Recipe(
            name: "Bolo de rolo", category: .dessert,
            ingredients: []),
        "Chocolate Crackles": Recipe(
            name: "Chocolate crackles", category: .dessert,
            ingredients: []),
        "Crème Brûlée": Recipe(
            name: "Crème brûlée", category: .dessert,
            ingredients: []),
        "Fruit Pie Filling": Recipe(
            name: "Fruit Pie Filling", category: .dessert,
            ingredients: []),
        "Kanom Thong Ek": Recipe(
            name: "Kanom Thong Ek", category: .dessert,
            ingredients: []),
        "Mochi": Recipe(
            name: "Mochi", category: .dessert,
            ingredients: []),
        "Marzipan": Recipe(
            name: "Marzipan", category: .dessert,
            ingredients: []),
        "Pie Crust": Recipe(
            name: "Pie Crust", category: .dessert,
            ingredients: Ingredient.fromLines(pieCrust)),
        "Shortbread Biscuits": Recipe(
            name: "Shortbread Biscuits", category: .dessert,
            ingredients: []),
        "Tiramisu": Recipe(
            name: "Tiramisu", category: .dessert,
            ingredients: []),
        "Crêpe": Recipe(
            name: "Crêpe", category: .pancake, ingredients: []),
        "Jianbing": Recipe(
            name: "Jianbing", category: .pancake, ingredients: []),
        "American": Recipe(
            name: "American", category: .pancake, ingredients: []),
        "Dosa": Recipe(
            name: "Dosa", category: .pancake, ingredients: []),
        "Injera": Recipe(
            name: "Injera", category: .pancake, ingredients: []),
        "Acar": Recipe(
            name: "Acar", category: .salad, ingredients: []),
        "Ambrosia": Recipe(
            name: "Ambrosia", category: .salad, ingredients: []),
        "Bok l'hong": Recipe(
            name: "Bok l'hong", category: .salad, ingredients: []),
        "Caprese": Recipe(
            name: "Caprese", category: .salad, ingredients: []),
        "Ceviche": Recipe(
            name: "Ceviche", category: .salad, ingredients: []),
        "Çoban salatası": Recipe(
            name: "Çoban salatası", category: .salad, ingredients: []),
        "Fiambre": Recipe(
            name: "Fiambre", category: .salad, ingredients: []),
        "Kachumbari": Recipe(
            name: "Kachumbari", category: .salad, ingredients: []),
        "Niçoise": Recipe(
            name: "Niçoise", category: .salad, ingredients: []),
    ]

    recipes["Apple Pie"]!.related = [
        recipes["Pie Crust"]!.id,
        recipes["Fruit Pie Filling"]!.id,
    ]

    recipes["Pie Crust"]!.related = [recipes["Fruit Pie Filling"]!.id]
    recipes["Fruit Pie Filling"]!.related = [recipes["Pie Crust"]!.id]

    return Array(recipes.values)
}()

let applePie = """
    ¾ cup white sugar
    2 tablespoons all-purpose flour
    ½ teaspoon ground cinnamon
    ¼ teaspoon ground nutmeg
    ½ teaspoon lemon zest
    7 cups thinly sliced apples
    2 teaspoons lemon juice
    1 tablespoon butter
    1 recipe pastry for a 9 inch double crust pie
    4 tablespoons milk
    """

let pieCrust = """
    2 ½ cups all purpose flour
    1 Tbsp. powdered sugar
    1 tsp. sea salt
    ½ cup shortening
    ½ cup butter (Cold, Cut Into Small Pieces)
    ⅓ cup cold water (Plus More As Needed)
    """

struct MultipleColumns_Previews: PreviewProvider {
    static var previews: some View {
        MultipleColumns()
    }
}

14:10 - Multiple Columns with a Stack

import SwiftUI

// Multiple columns with a stack
struct MultipleColumnsWithStack: View {
    @State private var selectedCategory: Category?
    @State private var path: [Recipe] = []
    @StateObject private var dataModel = DataModel()

    var body: some View {
        NavigationSplitView {
            List(Category.allCases, selection: $selectedCategory) { category in
                NavigationLink(category.localizedName, value: category)
            }
            .navigationTitle("Categories")
        } detail: {
            NavigationStack(path: $path) {
                RecipeGrid(category: selectedCategory)
            }
        }
        .environmentObject(dataModel)
    }
}

struct RecipeGrid: View {
    @EnvironmentObject private var dataModel: DataModel
    var category: Category?

    var body: some View {
        if let category = category {
            ScrollView {
                LazyVGrid(columns: columns) {
                    ForEach(dataModel.recipes(in: category)) { recipe in
                        NavigationLink(value: recipe) {
                            RecipeTile(recipe: recipe)
                        }
                    }
                }
            }
            .navigationTitle(category.localizedName)
            .navigationDestination(for: Recipe.self) { recipe in
                RecipeDetail(recipe: recipe)
            }
        } else {
            Text("Select a category")
        }
    }

    var columns: [GridItem] { [GridItem(.adaptive(minimum: 240))] }
}

struct RecipeDetail: View {
    @EnvironmentObject private var dataModel: DataModel
    var recipe: Recipe

    var body: some View {
        Text("Recipe details go here")
            .navigationTitle(recipe.name)
        ForEach(recipe.related.compactMap { dataModel[$0] }) { related in
            NavigationLink(related.name, value: related)
        }
    }
}

struct RecipeTile: View {
    var recipe: Recipe

    var body: some View {
        VStack {
            Rectangle()
                .fill(Color.secondary.gradient)
                .frame(width: 240, height: 240)
            Text(recipe.name)
                .lineLimit(2, reservesSpace: true)
                .font(.headline)
        }
        .tint(.primary)
    }
}

class DataModel: ObservableObject {
    @Published var recipes: [Recipe] = builtInRecipes

    func recipes(in category: Category?) -> [Recipe] {
        recipes
            .filter { $0.category == category }
            .sorted { $0.name < $1.name }
    }

    subscript(recipeId: Recipe.ID) -> Recipe? {
        // A real app would want to maintain an index from identifiers to
        // recipes.
        recipes.first { recipe in
            recipe.id == recipeId
        }
    }
}

enum Category: Int, Hashable, CaseIterable, Identifiable, Codable {
    case dessert
    case pancake
    case salad
    case sandwich

    var id: Int { rawValue }

    var localizedName: LocalizedStringKey {
        switch self {
        case .dessert:
            return "Dessert"
        case .pancake:
            return "Pancake"
        case .salad:
            return "Salad"
        case .sandwich:
            return "Sandwich"
        }
    }
}

struct Recipe: Hashable, Identifiable {
    let id = UUID()
    var name: String
    var category: Category
    var ingredients: [Ingredient]
    var related: [Recipe.ID] = []
    var imageName: String? = nil
}

struct Ingredient: Hashable, Identifiable {
    let id = UUID()
    var description: String

    static func fromLines(_ lines: String) -> [Ingredient] {
        lines.split(separator: "\n", omittingEmptySubsequences: true)
            .map { Ingredient(description: String($0)) }
    }
}

let builtInRecipes: [Recipe] = {
    var recipes = [
        "Apple Pie": Recipe(
            name: "Apple Pie", category: .dessert,
            ingredients: Ingredient.fromLines(applePie)),
        "Baklava": Recipe(
            name: "Baklava", category: .dessert,
            ingredients: []),
        "Bolo de Rolo": Recipe(
            name: "Bolo de rolo", category: .dessert,
            ingredients: []),
        "Chocolate Crackles": Recipe(
            name: "Chocolate crackles", category: .dessert,
            ingredients: []),
        "Crème Brûlée": Recipe(
            name: "Crème brûlée", category: .dessert,
            ingredients: []),
        "Fruit Pie Filling": Recipe(
            name: "Fruit Pie Filling", category: .dessert,
            ingredients: []),
        "Kanom Thong Ek": Recipe(
            name: "Kanom Thong Ek", category: .dessert,
            ingredients: []),
        "Mochi": Recipe(
            name: "Mochi", category: .dessert,
            ingredients: []),
        "Marzipan": Recipe(
            name: "Marzipan", category: .dessert,
            ingredients: []),
        "Pie Crust": Recipe(
            name: "Pie Crust", category: .dessert,
            ingredients: Ingredient.fromLines(pieCrust)),
        "Shortbread Biscuits": Recipe(
            name: "Shortbread Biscuits", category: .dessert,
            ingredients: []),
        "Tiramisu": Recipe(
            name: "Tiramisu", category: .dessert,
            ingredients: []),
        "Crêpe": Recipe(
            name: "Crêpe", category: .pancake, ingredients: []),
        "Jianbing": Recipe(
            name: "Jianbing", category: .pancake, ingredients: []),
        "American": Recipe(
            name: "American", category: .pancake, ingredients: []),
        "Dosa": Recipe(
            name: "Dosa", category: .pancake, ingredients: []),
        "Injera": Recipe(
            name: "Injera", category: .pancake, ingredients: []),
        "Acar": Recipe(
            name: "Acar", category: .salad, ingredients: []),
        "Ambrosia": Recipe(
            name: "Ambrosia", category: .salad, ingredients: []),
        "Bok l'hong": Recipe(
            name: "Bok l'hong", category: .salad, ingredients: []),
        "Caprese": Recipe(
            name: "Caprese", category: .salad, ingredients: []),
        "Ceviche": Recipe(
            name: "Ceviche", category: .salad, ingredients: []),
        "Çoban salatası": Recipe(
            name: "Çoban salatası", category: .salad, ingredients: []),
        "Fiambre": Recipe(
            name: "Fiambre", category: .salad, ingredients: []),
        "Kachumbari": Recipe(
            name: "Kachumbari", category: .salad, ingredients: []),
        "Niçoise": Recipe(
            name: "Niçoise", category: .salad, ingredients: []),
    ]

    recipes["Apple Pie"]!.related = [
        recipes["Pie Crust"]!.id,
        recipes["Fruit Pie Filling"]!.id,
    ]

    recipes["Pie Crust"]!.related = [recipes["Fruit Pie Filling"]!.id]
    recipes["Fruit Pie Filling"]!.related = [recipes["Pie Crust"]!.id]

    return Array(recipes.values)
}()

let applePie = """
    ¾ cup white sugar
    2 tablespoons all-purpose flour
    ½ teaspoon ground cinnamon
    ¼ teaspoon ground nutmeg
    ½ teaspoon lemon zest
    7 cups thinly sliced apples
    2 teaspoons lemon juice
    1 tablespoon butter
    1 recipe pastry for a 9 inch double crust pie
    4 tablespoons milk
    """

let pieCrust = """
    2 ½ cups all purpose flour
    1 Tbsp. powdered sugar
    1 tsp. sea salt
    ½ cup shortening
    ½ cup butter (Cold, Cut Into Small Pieces)
    ⅓ cup cold water (Plus More As Needed)
    """

struct MultipleColumnsWithStack_Previews: PreviewProvider {
    static var previews: some View {
        MultipleColumnsWithStack()
    }
}

18:12 - Use Scene Storage

import SwiftUI
import Combine
import Foundation

// Use SceneStorage to save and restore
struct UseSceneStorage: View {
    @StateObject private var navModel = NavigationModel()
    @SceneStorage("navigation") private var data: Data?
    @StateObject private var dataModel = DataModel()

    var body: some View {
        NavigationSplitView {
            List(
                Category.allCases, selection: $navModel.selectedCategory
            ) { category in
                NavigationLink(category.localizedName, value: category)
            }
            .navigationTitle("Categories")
        } detail: {
            NavigationStack(path: $navModel.recipePath) {
                RecipeGrid(category: navModel.selectedCategory)
            }
        }
        .task {
            if let data = data {
                navModel.jsonData = data
            }
            for await _ in navModel.objectWillChangeSequence {
                data = navModel.jsonData
            }
        }
        .environmentObject(dataModel)
    }
}

// Make the navigation model Codable
class NavigationModel: ObservableObject, Codable {
    @Published var selectedCategory: Category?
    @Published var recipePath: [Recipe] = []

    enum CodingKeys: String, CodingKey {
        case selectedCategory
        case recipePathIds
    }

    func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)
        try container.encodeIfPresent(selectedCategory, forKey: .selectedCategory)
        try container.encode(recipePath.map(\.id), forKey: .recipePathIds)
    }

    init() {}

    required init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        self.selectedCategory = try container.decodeIfPresent(
            Category.self, forKey: .selectedCategory)

        let recipePathIds = try container.decode([Recipe.ID].self, forKey: .recipePathIds)
        self.recipePath = recipePathIds.compactMap { DataModel.shared[$0] }
    }

    var jsonData: Data? {
        get {
            try? JSONEncoder().encode(self)
        }
        set {
            guard let data = newValue,
                  let model = try? JSONDecoder().decode(NavigationModel.self, from: data)
            else { return }
            self.selectedCategory = model.selectedCategory
            self.recipePath = model.recipePath

        }
    }

    var objectWillChangeSequence:
        AsyncPublisher<Publishers.Buffer<ObservableObjectPublisher>>
    {
        objectWillChange
            .buffer(size: 1, prefetch: .byRequest, whenFull: .dropOldest)
            .values
    }
}

struct RecipeGrid: View {
    var category: Category?
    @EnvironmentObject private var dataModel: DataModel

    var body: some View {
        if let category = category {
            ScrollView {
                LazyVGrid(columns: columns) {
                    ForEach(dataModel.recipes(in: category)) { recipe in
                        NavigationLink(value: recipe) {
                            RecipeTile(recipe: recipe)
                        }
                    }
                }
            }
            .navigationTitle(category.localizedName)
            .navigationDestination(for: Recipe.self) { recipe in
                RecipeDetail(recipe: recipe)
            }
        } else {
            Text("Select a category")
        }
    }

    var columns: [GridItem] { [GridItem(.adaptive(minimum: 240))] }
}

struct RecipeDetail: View {
    @EnvironmentObject private var dataModel: DataModel
    var recipe: Recipe

    var body: some View {
        Text("Recipe details go here")
            .navigationTitle(recipe.name)
        ForEach(recipe.related.compactMap { dataModel[$0] }) { related in
            NavigationLink(related.name, value: related)
        }
    }
}

struct RecipeTile: View {
    var recipe: Recipe

    var body: some View {
        VStack {
            Rectangle()
                .fill(Color.secondary.gradient)
                .frame(width: 240, height: 240)
            Text(recipe.name)
                .lineLimit(2, reservesSpace: true)
                .font(.headline)
        }
        .tint(.primary)
    }
}

class DataModel: ObservableObject {
    @Published var recipes: [Recipe] = builtInRecipes

    static var shared: DataModel {
        // Just instantiate each time for the example. A real app would need to
        // persist the data model as well.
        DataModel()
    }

    func recipes(in category: Category?) -> [Recipe] {
        recipes
            .filter { $0.category == category }
            .sorted { $0.name < $1.name }
    }

    subscript(recipeId: Recipe.ID) -> Recipe? {
        // A real app would want to maintain an index from identifiers to
        // recipes.
        recipes.first { recipe in
            recipe.id == recipeId
        }
    }
}

enum Category: Int, Hashable, CaseIterable, Identifiable, Codable {
    case dessert
    case pancake
    case salad
    case sandwich

    var id: Int { rawValue }

    var localizedName: LocalizedStringKey {
        switch self {
        case .dessert:
            return "Dessert"
        case .pancake:
            return "Pancake"
        case .salad:
            return "Salad"
        case .sandwich:
            return "Sandwich"
        }
    }
}

struct Recipe: Hashable, Identifiable {
    let id: UUID
    var name: String
    var category: Category
    var ingredients: [Ingredient]
    var related: [Recipe.ID] = []
    var imageName: String? = nil
}

struct Ingredient: Hashable, Identifiable {
    let id = UUID()
    var description: String

    static func fromLines(_ lines: String) -> [Ingredient] {
        lines.split(separator: "\n", omittingEmptySubsequences: true)
            .map { Ingredient(description: String($0)) }
    }
}

let builtInRecipes: [Recipe] = {
    var recipes = [
        "Apple Pie": Recipe(
            id: UUID(uuidString: "E35A5C9C-F1EA-4B3D-9980-E2240B363AC8")!,
            name: "Apple Pie", category: .dessert,
            ingredients: Ingredient.fromLines(applePie)),
        "Baklava": Recipe(
            id: UUID(uuidString: "B95B2D99-F45D-4B74-9EC4-526914FFC414")!,
            name: "Baklava", category: .dessert,
            ingredients: []),
        "Bolo de Rolo": Recipe(
            id: UUID(uuidString: "E17C729D-1E09-48F6-99E2-5BB959F5AE70")!,
            name: "Bolo de Rolo", category: .dessert,
            ingredients: []),
        "Chocolate Crackles": Recipe(
            id: UUID(uuidString: "89202A12-2B04-4EFE-ADC5-D1ECE7A25389")!,
            name: "Chocolate Crackles", category: .dessert,
            ingredients: []),
        "Crème Brûlée": Recipe(
            id: UUID(uuidString: "412EA92A-40B5-4CFE-9379-627A1C80FFE1")!,
            name: "Crème Brûlée", category: .dessert,
            ingredients: []),
        "Fruit Pie Filling": Recipe(
            id: UUID(uuidString: "4792C8AE-9596-4502-A9CB-806E2DFEA408")!,
            name: "Fruit Pie Filling", category: .dessert,
            ingredients: []),
        "Kanom Thong Ek": Recipe(
            id: UUID(uuidString: "331C25F6-4FED-4DA5-980E-7E619855DE92")!,
            name: "Kanom Thong Ek", category: .dessert,
            ingredients: []),
        "Mochi": Recipe(
            id: UUID(uuidString: "1EAA5288-8D2B-4969-AF97-ED591796B456")!,
            name: "Mochi", category: .dessert,
            ingredients: []),
        "Marzipan": Recipe(
            id: UUID(uuidString: "416F4F5A-A81C-40FD-87F1-060B0F57DE6D")!,
            name: "Marzipan", category: .dessert,
            ingredients: []),
        "Pie Crust": Recipe(
            id: UUID(uuidString: "D0820C1A-1AFB-4472-97DA-39A475304048")!,
            name: "Pie Crust", category: .dessert,
            ingredients: Ingredient.fromLines(pieCrust)),
        "Shortbread Biscuits": Recipe(
            id: UUID(uuidString: "3D9FEA8C-B38E-4739-8B4B-424885D76926")!,
            name: "Shortbread Biscuits", category: .dessert,
            ingredients: []),
        "Tiramisu": Recipe(
            id: UUID(uuidString: "586B9A4C-410A-40D2-AE40-BC32351A5C08")!,
            name: "Tiramisu", category: .dessert,
            ingredients: []),
        "Crêpe": Recipe(
            id: UUID(uuidString: "9BD6C3B2-30CB-425E-8D60-7F07D0BA720C")!,
            name: "Crêpe", category: .pancake,
            ingredients: []),
        "Jianbing": Recipe(
            id: UUID(uuidString: "117E5CD4-8FF9-43FB-ACAE-53C35A648F6F")!,
            name: "Jianbing", category: .pancake,
            ingredients: []),
        "American": Recipe(
            id: UUID(uuidString: "4584B877-E482-4FF2-824E-FC667BFAD271")!,
            name: "American", category: .pancake,
            ingredients: []),
        "Dosa": Recipe(
            id: UUID(uuidString: "5666FEB6-90DB-4CD2-91FA-D6F00986E90E")!,
            name: "Dosa", category: .pancake,
            ingredients: []),
        "Injera": Recipe(
            id: UUID(uuidString: "752DAEB8-123E-4C48-A190-79742AA56869")!,
            name: "Injera", category: .pancake,
            ingredients: []),
        "Acar": Recipe(
            id: UUID(uuidString: "F0D54AF2-04AD-4F08-ACE4-7886FCAE1F7B")!,
            name: "Acar", category: .salad,
            ingredients: []),
        "Ambrosia": Recipe(
            id: UUID(uuidString: "F7FD59E8-F1AE-4331-8667-D5534817F7E7")!,
            name: "Ambrosia", category: .salad,
            ingredients: []),
        "Bok L'hong": Recipe(
            id: UUID(uuidString: "3DE38C07-F985-4E05-810C-1108A777766B")!,
            name: "Bok L'hong", category: .salad,
            ingredients: []),
        "Caprese": Recipe(
            id: UUID(uuidString: "055D963C-0546-4578-AF18-6FBEE249EF35")!,
            name: "Caprese", category: .salad,
            ingredients: []),
        "Ceviche": Recipe(
            id: UUID(uuidString: "50B62AF4-89AF-4D00-9832-E200FEC01279")!,
            name: "Ceviche", category: .salad,
            ingredients: []),
        "Çoban Salatası": Recipe(
            id: UUID(uuidString: "87AD6B33-FFD2-4E5C-BC4B-59769F7AC7E3")!,
            name: "Çoban Salatası", category: .salad,
            ingredients: []),
        "Fiambre": Recipe(
            id: UUID(uuidString: "8A9BC0D5-A931-4381-BDA8-713DF6389FE7")!,
            name: "Fiambre", category: .salad,
            ingredients: []),
        "Kachumbari": Recipe(
            id: UUID(uuidString: "E9497D38-49E0-4A18-939B-63A3F2C7C0B4")!,
            name: "Kachumbari", category: .salad,
            ingredients: []),
        "Niçoise": Recipe(
            id: UUID(uuidString: "DE9F7106-4D0C-4EAC-B44C-A8D8ECD81087")!,
            name: "Niçoise", category: .salad,
            ingredients: [])
    ]

    recipes["Apple Pie"]!.related = [
        recipes["Pie Crust"]!.id,
        recipes["Fruit Pie Filling"]!.id
    ]

    recipes["Pie Crust"]!.related = [recipes["Fruit Pie Filling"]!.id]
    recipes["Fruit Pie Filling"]!.related = [recipes["Pie Crust"]!.id]

    return Array(recipes.values)
}()

let applePie = """
    ¾ cup white sugar
    2 tablespoons all-purpose flour
    ½ teaspoon ground cinnamon
    ¼ teaspoon ground nutmeg
    ½ teaspoon lemon zest
    7 cups thinly sliced apples
    2 teaspoons lemon juice
    1 tablespoon butter
    1 recipe pastry for a 9 inch double crust pie
    4 tablespoons milk
    """

let pieCrust = """
    2 ½ cups all purpose flour
    1 Tbsp. powdered sugar
    1 tsp. sea salt
    ½ cup shortening
    ½ cup butter (Cold, Cut Into Small Pieces)
    ⅓ cup cold water (Plus More As Needed)
    """

struct UseSceneStorage_Previews: PreviewProvider {
    static var previews: some View {
        UseSceneStorage()
    }
}

25:33 - Biscuits

import SwiftUI

struct Biscuits: View {
    @State private var step = 0
    @ScaledMetric private var fontSize = 18

    var body: some View {
        VStack(alignment: .leading) {
            HStack {
                Spacer()
                VStack {
                    Text("Biscuits")
                        .font(.headline)
                    Text(subtitle)
                        .font(.subheadline)
                }
                .padding(16)
                Spacer()
            }
            Spacer()
            Text(LocalizedStringKey(steps[step]))
                .font(.system(
                    size: fontSize, weight: .semibold, design: .serif))
                .padding(16)
                .lineLimit(1...)
            Spacer()
            HStack {
                Button {
                    withAnimation {
                        step -= 1
                    }
                } label: {
                    Label("Previous", systemImage: "chevron.backward")
                }
                .disabled(step - 1 < 0)

                Spacer()

                Button {
                    withAnimation {
                        step += 1
                    }
                } label: {
                    Label("Next", systemImage: "chevron.forward")
                }
                .disabled(step + 1 >= steps.count)
            }
            .buttonStyle(CarouselButtonStyle())
            .padding(16)
        }
        .foregroundStyle(Color.white)
        .background(gradient)
        .ignoresSafeArea(edges: .bottom)
    }

    var subtitle: LocalizedStringKey {
        if step == 0 { return "Ingredients" }
        return "Step \(step)"
    }

    var gradient: AngularGradient {
        AngularGradient(
            colors: colors,
            center: UnitPoint(x: 0.5, y: 1.0),
            angle: .degrees(180 * Double(step) / Double(steps.count - 1)))
    }

}

struct CarouselButtonStyle: ButtonStyle {
    @Environment(\.isEnabled) private var isEnabled

    func makeBody(configuration: Configuration) -> some View {
        ZStack {
            Circle()
                .fill(.ultraThinMaterial.shadow(.inner(
                    radius: configuration.isPressed ? 3 : 0)))
                .frame(width: 44, height: 44)
            configuration.label
                .labelStyle(.iconOnly)
                .foregroundStyle(isEnabled ? .black : .secondary)
                .opacity(configuration.isPressed ? 0.3 : 0.8)
        }
    }
}

let steps = [
    """
    2 cups all-purpose flour
    ¼ teaspoons coarse salt
    1 cup (2 sticks) unsalted butter, room temperature
    ¾ cup confectioners' sugar
    """,
    "Sift flour and salt, mix into bowl and set aside.",
    "Mix butter on high speed until fluffy (3 to 5 minutes).",
    "Gradually add sugar slowly, continuing to mix until pale and fluffy.",
    "Add flour all at once and mix until combined.",
    "Butter a square pan.",
    "Pat and roll shortbread into pan no more than 1/2-inch thick.",
    "Refrigerate for at least 30 minutes.",
    "Preheat oven to 300 F.",
    "Cut chilled shortbread into squares.",
    """
    Bake until golden and make sure the middle is firm. \
    Approximately 45 to 60 minutes.
    """,
    "Cool completely. Re-slice them, if necessary, and serve.",
]

let colors = [Color.yellow, .red, .purple]

struct Biscuits_Previews: PreviewProvider {
    static var previews: some View {
        Biscuits()
    }
}

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