Question

在使用EnvironmentObject并在详细视图中将变量绑定到我的数据时，我遇到了一些麻烦。我相信真理之源是@EnvironmentObject var userData: UserData。在列表视图中点击一行时，该详细信息视图应显示所选项目，并且您应该能够通过weight.weightdate来修改DatePicker。应用程序会编译，当我使用下面的代码时，但是当我尝试使用类似DatePicker(selection: $userData.weights[weightIndex].day, in: ...Date(), displayedComponents: [.date,.hourAndMinute]) {之类的东西绑定到我的数据时，出现以下错误：

Type 'Any' has no member 'date'
Type 'Any' has no member 'hourAndMinute'

如果我添加 DatePickerComponents .date，我会在Text("Date")行上得到表达式类型不明确而没有更多上下文。

struct Weight: Hashable, Codable, Identifiable {
    var id: Int
    var weightdate: Date
    var weight: Float = 0
    ...
}
struct WeightDetail: View {
    @EnvironmentObject var userData: UserData
    var weight: Weight
    var weightIndex: Int {
           userData.weights.firstIndex(where: { $0.id == weight.id })!
       }

    @State private var selectedDay = Date()

    var body: some View {
        Form {
            Section {
                //DatePicker(selection: $userData.weights[weightIndex].day, in: ...Date(), displayedComponents: [.date,.hourAndMinute]) {
                //ERROR Type 'Any' has no member 'date'
                //ERROR Type 'Any' has no member 'hourAndMinute'

                DatePicker(selection: $selectedDay, in: ...Date(), displayedComponents: [.date,.hourAndMinute]) {
                    Text("Date")
                    //also works: Text("\(weight.weightdate)")
                }
            }
            ...

Answer 1

我对数据做了一些假设。看现场的代表。它应该提供有关环境对象的一些想法。

import SwiftUI

struct ContentView: View {
    var body: some View {

            WeightDetail(weight: Weight(id: 0, weightdate: Date()))
    }
}


struct WeightDetail: View {
    @EnvironmentObject var userData: UserData
      var weight: Weight
    var weightIndex: Int {
                userData.weights.firstIndex(where: { $0.id == weight.id })!
        }

    @State private var selectedDay = Date()

    var body: some View {
        Form {
            Section {
              //  DatePicker(selection: $userData.weights[weightIndex].day, in: ...Date(), displayedComponents: [.date,.hourAndMinute])

                            DatePicker(selection: $userData.weights[weightIndex].weightdate, in: ...Date(), displayedComponents: [.date, .hourAndMinute] ) {
                                Text("Display")
                            }
                                //{
                //ERROR Type 'Any' has no member 'date'
                //ERROR Type 'Any' has no member 'hourAndMinute'

//                DatePicker(selection: $selectedDay, in: ...Date(), displayedComponents: [.date,.hourAndMinute]) {
//                    Text("Date")
//                    //also works: Text("\(weight.weightdate)")
//                }
            }
            }

    }

}


struct Weight: Hashable, Codable, Identifiable {
    var id: Int
    var weightdate: Date
    var weight: Float = 0
}

class UserData: ObservableObject {

    @Published var weights = [Weight]()

    init(weights: [Weight]){
        self.weights = weights
    }
}

SceneDelegate：

class SceneDelegate: UIResponder, UIWindowSceneDelegate {

    var window: UIWindow?
    var userData: UserData!


    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {

        let weight = Weight(id: 0, weightdate:  Date().advanced(by: -100000))
        let weights = [weight]
        userData =  UserData(weights: weights)

        let contentView = ContentView().environmentObject(userData)


        // Use a UIHostingController as window root view controller.
        if let windowScene = scene as? UIWindowScene {
            let window = UIWindow(windowScene: windowScene)
            window.rootViewController = UIHostingController(rootView: contentView)
            self.window = window
            window.makeKeyAndVisible()
        }
    }
}

将DatePicker绑定到我的EnvironmentObject变量时遇到问题

1 个答案: