ساخت لیست پیشرفته در SwiftUI — از صفر تا صد

1enum ListState {
2    case error(_ error: Error?)
3    case items
4    case loading
5}
6extension ListState {
7    var error: Error? {
8        switch self {
9            case .error(let error):
10                return error
11            default:
12                return nil
13        }
14    }
15}

1final class ListService: BindableObject {
2    private(set) var items: [AnyListItem] = [] {
3        didSet {
4            didChange.send()
5        }
6    }
7    
8    private(set) var didChange = PassthroughSubject<Void, Never>()
9    
10    var listState: ListState = .items {
11        didSet {
12            didChange.send()
13        }
14    }
15    
16    func appendItems<Item: Identifiable>(_ items: [Item]) where Item: View {
17        let anyListItems = items.map { AnyListItem(item: $0) }
18        self.items.append(contentsOf: anyListItems)
19    }
20    
21    func updateItems<Item: Identifiable>(_ items: [Item]) where Item: View {
22        let anyListItems = items.map { AnyListItem(item: $0) }
23        for anyListItem in anyListItems {
24            guard let itemIndex = self.items.firstIndex(where: { $0.id == anyListItem.id }) else {
25                continue
26            }
27            
28            self.items[itemIndex] = anyListItem
29        }
30    }
31    
32    func removeItems<Item: Identifiable>(_ items: [Item]) where Item: View {
33        let anyListItemsToRemove = items.map { AnyListItem(item: $0) }
34        self.items.removeAll(where: { item in
35             return anyListItemsToRemove.contains { item.id == $0.id }
36        })
37    }
38    
39    func removeAllItems() {
40        items.removeAll()
41    }
42}

1struct AnyListItem: Identifiable, View {
2    let id: AnyHashable
3    let body: AnyView
4    
5    init<Item: Identifiable>(item: Item) where Item: View {
6        id = item.id
7        body = AnyView(item)
8    }
9}

1struct AdvancedList<EmptyStateView: View, ErrorStateView: View, LoadingStateView: View> : View {
2    @ObjectBinding private var listService: ListService
3    private let emptyStateView: () -> EmptyStateView
4    private let errorStateView: (Error?) -> ErrorStateView
5    private let loadingStateView: () -> LoadingStateView
6    
7    var body: some View {
8        return Group {
9            if listService.listState.error != nil {
10                errorStateView(listService.listState.error)
11            } else if listService.listState == .items {
12                if !listService.items.isEmpty {
13                    List(listService.items.identified(by: \.id)) { item in
14                        item
15                    }
16                } else {
17                    emptyStateView()
18                }
19            } else if listService.listState == .loading {
20                loadingStateView()
21            } else {
22                EmptyView()
23            }
24        }
25    }
26    
27    init(listService: ListService, @ViewBuilder emptyStateView: @escaping () -> EmptyStateView, @ViewBuilder errorStateView: @escaping (Error?) -> ErrorStateView, @ViewBuilder loadingStateView: @escaping () -> LoadingStateView) {
28        self.listService = listService
29        self.emptyStateView = emptyStateView
30        self.errorStateView = errorStateView
31        self.loadingStateView = loadingStateView
32    }
33}

1struct ContactListItem: Identifiable {
2    @State private var collapsed: Bool = true
3    
4    let id: String
5    let firstName: String
6    let lastName: String
7    let streetAddress: String
8    let zip: String
9    let city: String
10    
11    var viewRepresentationType: ContactListItemViewRepresentationType = .short
12}
13extension ContactListItem: View {
14    var body: some View {
15        Group {
16            if viewRepresentationType == .short {
17                ContactListItemView(firstName: firstName,
18                                    lastName: lastName,
19                                    hasMoreInformation: false)
20            } else if viewRepresentationType == .detail {
21                NavigationLink(destination: ContactDetailView(listItem: self), label: {
22                    ContactListItemView(firstName: firstName,
23                                        lastName: lastName,
24                                        hasMoreInformation: true)
25                })
26            } else if viewRepresentationType == .collapsable {
27                VStack {
28                    if collapsed {
29                        ContactListItemView(firstName: firstName,
30                                            lastName: lastName,
31                                            hasMoreInformation: false)
32                    } else {
33                        ContactDetailView(listItem: self)
34                    }
35                    
36                    Button(action: {
37                        self.collapsed.toggle()
38                    }) {
39                        Text("\(collapsed ? "show" : "hide") details")
40                    }.foregroundColor(.blue)
41                }
42            }
43        }
44    }
45}

1struct AdListItem: Identifiable {
2    @State private var isImageCollapsed: Bool = true
3    
4    let id: String
5    let text: String
6    var viewRepresentationType: AdListItemViewRepresentationType = .short
7}
8extension AdListItem: View {
9    var body: some View {
10        Group {
11            if viewRepresentationType == .short {
12                NavigationLink(destination: AdDetailView(text: text), label: {
13                    Text(text)
14                        .lineLimit(1)
15                    Text("ℹ️")
16                })
17            } else if viewRepresentationType == .long {
18                Text(text)
19                    .lineLimit(nil)
20            } else if viewRepresentationType == .image {
21                VStack {
22                    if !isImageCollapsed {
23                        Image("restaurant")
24                            .resizable()
25                            .aspectRatio(contentMode: .fit)
26                            .frame(height: 200)
27                    }
28                    
29                    Button(action: {
30                        self.isImageCollapsed.toggle()
31                    }) {
32                        Text("\(isImageCollapsed ? "show" : "hide") image")
33                    }.foregroundColor(.blue)
34                }
35            }
36        }
37    }
38}

1struct ContentView : View {
2    @ObjectBinding private var listService: ListService = ListService()
3    
4    var body: some View {
5        NavigationView {
6            return GeometryReader { geometry in
7                VStack {
8                    CustomListStateSegmentedControlView(listService: self.listService)
9                    
10                    AdvancedList(listService: self.listService, emptyStateView: {
11                        Text("No data")
12                    }, errorStateView: { error in
13                        Text("\(error?.localizedDescription ?? "Error")").lineLimit(nil)
14                    }, loadingStateView: {
15                        Text("Loading ...")
16                    })
17                    .frame(width: geometry.size.width)
18                }
19                .navigationBarTitle(Text("List of Items"))
20            }
21        }
22    }
23}