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

Question

我试图分配值从EnvironmentObject叫userSettings到名为类的实例categoryData ，试图将值赋给类这里的时候，我得到一个错误ObserverCategory(userID: self.userSettings.id)

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

接下来是我试图分配其值的代码：

//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 

            }
        }
    }
}

有人可以指导我解决这个错误吗？

谢谢

Answer 1

因为@EnvironmentObject和@ObservedObject同时初始化。 因此，您不能将其中一个用作另一个的论据。

你可以让ObservedObject更懒惰。 因此，您可以在它可用时将其与EnvironmentObject相关联。 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))
    }
}