SwiftUI 加载数据

Question

当我呈现 SwiftUI 视图时，我试图从 ObservableObject 类加载数据，但 我收到以下错误代码：“无法在属性初始化程序中使用实例成员 'documentID'；属性初始化程序在 'self' 之前运行可用”

数据查询类：

class ItemDataDelegate: ObservableObject {
    @Published var serviceContentLoaded = Bool()
    @Published var SelectedCategory: String?
    @Published var SelectedDocumentID: String?
    
    init(SelectedCategory: String, SelectedDocumentID: String){
        self.getSelectedContentData(Category: SelectedCategory, DocumentID: SelectedDocumentID) {
            self.getSelectedCompanyData(CUID: ContentData[indexPath.row].CompanyID) {
                print("data query completed")
            }
        }
    }
}

这是我在调用和完成之前代码中的数据时想要呈现的视图：

我上面提到的错误显示在@StateObject var itemDataDelegate = ItemDataDelegate(SelectedCategory: selectedCategory, SelectedDocumentID: documentID) 代码行。

struct DetailView: View {
    @Binding var documentID: String
    @Binding var selectedCategory: String
    @StateObject var itemDataDelegate = ItemDataDelegate(SelectedCategory: selectedCategory, SelectedDocumentID: documentID)
    @State private var showSheet = false
    @Environment(\.presentationMode) var mode: Binding<PresentationMode>
    
    var image: UIImage
    var companyName: String
    var cartActive: Bool
    
    var body: some View {
        return ZStack {
            switch itemDataDelegate.serviceContentLoaded {
                case true:
                    ContentView()
                case false:
                    LoadingView()
            }
        }
        .navigationBarHidden(true)
        .frame(maxWidth: .infinity, maxHeight: .infinity)
        .edgesIgnoringSafeArea(.all)
    }
}

Answer 1

由于您需要在@StateObject 的初始化中使用传入参数之一，因此您必须为您的View 编写一个自定义init。使用您当前的代码，它看起来像这样：

struct DetailView: View {
    @Binding var documentID: String
    @Binding var selectedCategory: String
    @StateObject var itemDataDelegate : ItemDataDelegate
    @State private var showSheet = false
    @Environment(\.presentationMode) var mode: Binding<PresentationMode>
    
    var image: UIImage
    var companyName: String
    var cartActive: Bool
    
    init(documentID: Binding<String>, selectedCategory: Binding<String>, image: UIImage, companyName: String, cartActive: Bool) {
        _documentID = documentID
        _selectedCategory = selectedCategory
        self.image = image
        self.companyName = companyName
        self.cartActive = cartActive
        _itemDataDelegate = StateObject(wrappedValue: ItemDataDelegate(SelectedCategory: selectedCategory.wrappedValue, SelectedDocumentID: documentID.wrappedValue))
    }
    
    var body: some View {
        return ZStack {
            switch itemDataDelegate.serviceContentLoaded {
                case true:
                    ContentView()
                case false:
                    LoadingView()
            }
        }
        .navigationBarHidden(true)
        .frame(maxWidth: .infinity, maxHeight: .infinity)
        .edgesIgnoringSafeArea(.all)
    }
}