如何将值从 EnvironmentObject 传递给 SwiftUI 中的类实例？

Question

我正在尝试将名为 userSettings 的 EnvironmentObject 中的值分配给名为 categoryData 的类实例，尝试将值分配给此处的类时出现错误 ObserverCategory(userID: self.userSettings.id)

错误说： Cannot use instance member 'userSettings' within property initializer; property initializers run before 'self' is available

这是我的代码：

这是我的环境对象类：

//user settings
final class UserSettings: ObservableObject {
    @Published var name : String = String()
    @Published var id : String = "12345"
}

接下来是我试图为其赋值的代码：

//user settings
@EnvironmentObject var userSettings: UserSettings

//instance of observer object
@ObservedObject var categoryData = ObserverCategory(userID: userSettings.id)

class ObserverCategory : ObservableObject {

    let userID : String

    init(userID: String) {

        let db = Firestore.firestore().collection("users/\(userID)/categories") //

        db.addSnapshotListener { (snap, err) in
            if err != nil {
                print((err?.localizedDescription)!)
                return
            }

            for doc in snap!.documentChanges {

                //code 

            }
        }
    }
}

谁能指导我解决这个错误？

谢谢

Answer 1

因为@EnvironmentObject 和@ObservedObject 正在同时初始化。所以你不能用其中一个作为另一个的论据。

您可以让ObservedObject 更懒惰。因此，当它可用时，您可以将其与EnvironmentObject 关联。例如：

struct CategoryView: View {

    //instance of observer object
    @ObservedObject var categoryData: ObserverCategory

    var body: some View { ,,, }
}

然后像这样传递它：

struct ContentView: View {

    //user settings
    @EnvironmentObject var userSettings: UserSettings

    var body: some View {
        CategoryView(categoryData: ObserverCategory(userID: userSettings.id))
    }
}