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

Question

I want to fill a list using a completion handler, the problem is that it's loading nil in the first execution and marks errors when I try to consume my View where I have my list that it's filled by completion handler... Any suggestions to fix this?
this is how I try to fill my list
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))
}
as you can see I would need to fill my list until InvitationService Request ends but If I try to put it inside the code I got a
Escaping closure captures mutating 'self' parameter
error
I mean
invitationService.getInvitations(id: userId, completionHandler: { (appointment) in
if appointment != nil{
appointmentList = appointment
self._invitationsList = State<[Appointment]?>.init(initialValue: (appointmentList))
}
})
My VIEW
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)
}
}
I'm trying to execute and when I do that invitationsList is nil

Answer 1

I recommend do not put such things into View.init, because SwiftUI view is struct, value, and can be re-created several times during layout/rendering. The better approach is to do this after view appeared (or, what is better, outside view hierarchy at all).
Anyway being in view here is possible approach
...
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
}
}
}