如何使用完成处理程序填充列表 [SWIFT UI]

Question

我想使用完成处理程序填充列表，问题是它在第一次执行时加载 nil 并在我尝试使用我的视图时标记错误，我的列表由完成处理程序填充。 . 有什么解决这个问题的建议吗？

这就是我尝试填写列表的方式

let invitationService: InvitationService = InvitationService()
@State private var invitationsList : [Appointment]?

init() {
    let defaults = UserDefaults.standard
    let userId = defaults.integer(forKey: "userId")
    var appointmentList : [Appointment]?

    invitationService.getInvitations(id: userId, completionHandler: { (appointment) in
        if appointment != nil{
            appointmentList = appointment
        }
    })

    _invitationsList = State<[Appointment]?>.init(initialValue: (appointmentList))
}

如您所见，我需要填写我的列表，直到 InvitationService 请求结束，但如果我尝试将其放入代码中，我会得到一个

Escaping closure captures mutating 'self' parameter

错误

我是说

  invitationService.getInvitations(id: userId, completionHandler: { (appointment) in
            if appointment != nil{
                appointmentList = appointment
                self._invitationsList = State<[Appointment]?>.init(initialValue: (appointmentList))
            }
        })

我的观点

var body: some View {
    NavigationView{

    ZStack{
        colors["LightGray"]?.edgesIgnoringSafeArea(.all)
        Text("Hey").onAppear(){
            let defaults = UserDefaults.standard
                                   let userId = defaults.integer(forKey: "userId")

                                   self.invitationService.getInvitations(id: userId) { (appointment) in
                                       self.invitationsList = appointment

                                   }
        }
        List {

            ForEach(invitationsList!, id: \.self){invitation in
                NavigationLink(destination: InvitationDetailView(invitation: invitation)){
                    HStack{
                        VStack(alignment: .center){
                            Text(invitation.startDate.prefix(2))
                                .font(.largeTitle)
                            Text(invitation.startDate[2..<6]).font(.subheadline)

                        }.padding()
                        Spacer().frame(width:UIScreen.main.bounds.width/15, alignment: .leading)

                        ImageView(withURL: invitation.imageProfile,widthValue: 80, heightValue: 80)
                            .aspectRatio(contentMode: .fit)
                            .clipShape(Circle())
                        Spacer()
                        VStack(alignment: .leading){
                            Text(invitation.titleVisit)
                                .font(.headline)
                                .frame(width: UIScreen.main.bounds.width/3, alignment: .leading)
                            Text(invitation.typeVisit)
                                .font(.footnote)
                            Text(invitation.startDate.suffix(9))
                                .font(.caption)
                        }.padding()
                    }
                    .background(self.colors["White"])
                    .cornerRadius(25)
                    .foregroundColor(self.colors["Black"])
                    .shadow(radius: 2, x: 0, y: 0)
                }



            }.onDelete(perform: delete)



        }


    }.hideNavigationBar(text: "back".localized)
}

}

我正在尝试执行，当我这样做时 invitationsList 为零

Answer 1

我建议不要把这样的东西放到View.init，因为SwiftUI视图是struct，value，并且可以在layout/rendering期间重新创建几次。更好的方法是在视图出现后执行此操作（或者，更好的是，根本不在视图层次结构之外）。

不管怎样，在这里查看是可能的方法

...
let invitationService: InvitationService = InvitationService()
@State private var invitationsList : [Appointment]? = nil

// nothing for init in this case

var body: some View {
    Text("Any subview here")
    .onAppear {
       let defaults = UserDefaults.standard
       let userId = defaults.integer(forKey: "userId")

       self.invitationService.getInvitations(id: userId) { (appointment) in
           self.invitationsList = appointment
       }
    }
}

如何使用完成处理程序填充列表 [SWIFT UI]

How to fill a list using Completion Handlers [SWIFT UI]

completionhandler

mutating-function

swiftui

swift5.2