我正在尝试重新创建 session 204 中演示的 SwiftUI 项目,但遇到了一些特殊问题。
我是通过观看这里的 session 写下这篇文章的:https://developer.apple.com/videos/play/wwdc2019/204
这是我的代码-
ContentView.swift:
import SwiftUI
struct ContentView : View {
@ObjectBinding var store = RoomStore()
var body: some View {
NavigationView {
List {
Section {
Button(action: addRoom) {
Text("Add Room")
}
}
Section {
ForEach(store.rooms) { room in //Error: Cannot convert value of type '(Room) -> RoomCell' to expected argument type '(_) -> _'
RoomCell(room: room)
}
.onDelete(perform: delete)
.onMove(perform: move)
}
}
.navigationBarTitle(Text("Rooms") )
.NavigationBarItems(trailing: EditButton())
.listStyle(.grouped)
}
}
func addRoom() {
store.rooms.append(Room(name: "Hall 2", capacity: 2000))
}
func delete(at offsets: IndexSet) {
store.rooms.remove(atOffsets: offsets) //Error: Incorrect argument label in call (have 'atOffsets:', expected 'at:')
}
func move(from source: IndexSet, to destination: Int) {
store.rooms.move(fromOffsets: source, toOffset: destination) //Error: Value of type '[Room]' has no member 'move'; did you mean 'remove'?
}
}
#if DEBUG
struct ContentView_Previews : PreviewProvider {
static var previews: some View {
Group {
ContentView(store: RoomStore(rooms: testData))
ContentView(store: RoomStore(rooms: testData))
.environment(\.sizeCategory, .extraExtraExtraLarge)
ContentView(store: RoomStore(rooms: testData))
.environment(\.colorScheme, .dark)
ContentView(store: RoomStore(rooms: testData))
.environment(\.layoutDirection, .rightToLeft)
.environment(\.locale, Locale(identifier: "ar"))
}
}
}
#endif
struct RoomCell : View {
let room: Room
var body: some View {
return NavigationButton(destination: RoomDetail(room: room) )
{
Image(room.thumbnailName)
.cornerRadius(8)
VStack(alignment: .leading) {
Text (room.name)
Text ("\(room.capacity) peopje")
.font(.subheadline)
.foregroundColor(.secondary)
}
}
}
}
房间.swift:
import SwiftUI
struct Room {
var id = UUID()
var name: String
var capacity: Int
var hasVideo: Bool = false
var imageName: String { return name }
var thumbnailName: String { return name + "Thumb" }
}
#if DEBUG
let testData = [
Room(name: "Observation Deck", capacity: 6, hasVideo: true),
Room(name: "Executive Suite", capacity: 8, hasVideo: false),
Room(name: "Charter Jet", capacity: 16, hasVideo: true),
Room(name: "Dungeon", capacity: 10, hasVideo: true),
Room(name: "Panorama", capacity: 12, hasVideo: false),
Room(name: "Oceanfront", capacity: 8, hasVideo: false),
Room(name: "Rainbow Room", capacity: 10, hasVideo: true),
Room(name: "Pastoral", capacity: 7, hasVideo: false),
Room(name: "Elephant Room", capacity: 1, hasVideo: false),
]
#endif
房间细节.swift:
import SwiftUI
struct RoomDetail : View {
let room: Room
@State private var zoomed = false
var body: some View { //Error: Function declares an opaque return type, but has no return statements in its body from which to infer an underlying type
ZStack(alignment: .topLeading) {
Image(room.imageName )
.resizable()
.aspectRatio(contentMode: zoomed ? .fill : .fit)
.navigationBarTitle(Text(room.name), displayMode:
.inline)
.tapAction { withAnimation(.basic(duration: 2)) {
self.zoomed.toggle() } }
}
.frame(minWidth: 0, maxWidth: .infinity, minHeight:
0, maxHeight: .infinity)
if room.hasVideo && !zoomed {
Image(systemName: "video. fill")
.font(.title)
.padding(.all)
.transition(.move(edge: .leading) )
}
}
}
#if DEBUG
struct RoomDetail_Previews : PreviewProvider {
static var previews: some View {
Group {
NavigationView { RoomDetail(room: testData[0]) }
NavigationView { RoomDetail(room: testData[1]) }
}
}
}
#endif
RoomStore.swift:
import SwiftUI
import Combine
class RoomStore : BindableObject {
var rooms: [Room] {
didSet { didChange.send(Void()) } //Solved
}
init(rooms: [Room] = []) {
self.rooms = rooms
}
var didChange = PassthroughSubject<Void, Never>()
}
错误消息包含在上下文中,作为注释,在上面的代码中。
最佳答案
对于此错误://错误:无法将类型“(Room) -> RoomCell”的值转换为预期的参数类型“(_) -> _” 像这样为您的列表模型实现可识别协议(protocol),
struct Room: Identifiable
对于这个://错误:调用中的参数标签不正确(有'atOffsets:',预期'at:') 我认为这不是你的问题:)但你可以使用这样的东西,
guard let index = Array(offset).first else { return }
store.rooms.remove(at: index)
对于这个://错误:类型“[Room]”的值没有成员“move”;您是说“删除”吗?和以前一样,您可以使用那段代码来移动
guard let sourceIndex = Array(source).first else { return }
store.rooms.insert(roomStore.rooms.remove(at: sourceIndex), at: destination)
您可以检查完整的源代码, https://github.com/ilyadaberdil/iOS-Samples/tree/master/SwiftUI-Sample
关于swift - 尝试从 WWDC session 重新创建基于 SwiftUI 的应用程序时出现问题,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/56487777/