如何將值從 EnvironmentObject 傳遞到 SwiftUI 中的類實例？

Question

我試圖分配值從EnvironmentObject叫userSettings到名為類的實例categoryData ，試圖將值賦給類這里的時候，我得到一個錯誤ObserverCategory(userID: self.userSettings.id)

錯誤說： 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

這是我的代碼：

這是我的環境對象類：

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

接下來是我試圖分配其值的代碼：

//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 

            }
        }
    }
}

有人可以指導我解決這個錯誤嗎？

謝謝

Answer 1

因為@EnvironmentObject和@ObservedObject同時初始化。 因此，您不能將其中一個用作另一個的論據。

你可以讓ObservedObject更懶惰。 因此，您可以在它可用時將其與EnvironmentObject相關聯。 例如：

struct CategoryView: View {

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

    var body: some View { ,,, }
}

然后像這樣傳遞它：

struct ContentView: View {

    //user settings
    @EnvironmentObject var userSettings: UserSettings

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