Update View Only After Aync Is Resolved with Completion Handler - swift

Question

I'm trying to update my view, only after the Async call is resolved. In the below code the arrayOfTodos.items comes in asynchronously a little after TodoListApp is rendered. The problem I'm having is that when onAppear runs, self.asyncTodoList.items is always empty since it hasn't received the values of the array yet from the network call. I'm stuck trying to figure out how to hold off on running onAppear until after the Promise is resolved, like with a completion handler?? And depending on the results of the network call, then modify the view. Thanks for any help! I've been stuck on this longer than I'll ever admit!
struct ContentView: View {
#StateObject var arrayOfTodos = AsyncGetTodosNetworkCall()
var body: some View {
TodoListApp(asyncTodoList: arrayOfTodos)
}
}
struct TodoListApp: View {
#ObservedObject var asyncTodoList: AsyncGetTodosNetworkCall
#State private var showPopUp: Bool = false
var body: some View {
NavigationView {
ZStack {
VStack {
Text("Top Area")
Text("List Area")
}
if self.showPopUp == true {
VStack {
Text("THIS IS MY POPUP!")
Text("No Items Added Yet")
}.frame(width: 300, height: 400)
}
}.onAppear {
let arrayItems = self.asyncTodoList
if arrayItems.items.isEmpty {
self.showPopUp = true
}
/*HERE! arrayItems.items.isEmpty is ALWAYS empty when onAppear
runs since it's asynchronous. What I'm trying to do is only
show the popup if the array is empty after the promise is
resolved.
What is happening is even if array resolved with multiple todos,
the popup is still showing because it was initially empty on
first run. */
}
}
}
}
class AsyncGetTodosNetworkCall: ObservableObject {
#AppStorage(DBUser.userID) var currentUserId: String?
private var REF_USERS = DB_BASE.collection(DBCOLLECTION.appUsers)
#Published var items = [TodoItem]()
func fetchTodos(toDetach: Bool) {
guard let userID = currentUserId else {
return
}
let userDoc = REF_USERS.document(String(userID))
.collection(DBCOLLECTION.todos)
.addSnapshotListener({ (querySnapshot, error) in
guard let documents = querySnapshot?.documents else {
print("No Documents Found")
return
}
self.items = documents.map { document -> TodoItem in
let todoID = document.documentID
let todoName = document.get(ToDo.todoName) as? String ?? ""
let todoCompleted = document.get(Todo.todoCompleted) as? Bool ?? false
return TodoItem(
id: todoID,
todoName: todoName,
todoCompleted: todoCompleted
)
}
})
if toDetach == true {
userDoc.remove()
}
}
}

Answer 1

While preparing my question, i found my own answer. Here it is in case someone down the road might run into the same issue.
struct ContentView: View {
#StateObject var arrayOfTodos = AsyncGetTodosNetworkCall()
#State var hasNoTodos: Bool = false
func getData() {
self.arrayOfTodos.fetchTodos(toDetach: false) { noTodos in
if noTodos {
self.hasNoTodos = true
}
}
}
func removeListeners() {
self.arrayOfTodos.fetchTodos(toDetach: true)
}
var body: some View {
TabView {
TodoListApp(asyncTodoList: arrayOfTodos, hasNoTodos : self.$hasNoTodos)
}.onAppear(perform: {
self.getData()
}).onDisappear(perform: {
self.removeListeners()
})
}
}
struct TodoListApp: View {
#ObservedObject var asyncTodoList: AsyncGetTodosNetworkCall
#Binding var hasNoTodos: Bool
#State private var hidePopUp: Bool = false
var body: some View {
NavigationView {
ZStack {
VStack {
Text("Top Area")
ScrollView {
LazyVStack {
ForEach(asyncTodoList.items) { item in
HStack {
Text("\(item.name)")
Spacer()
Text("Value")
}
}
}
}
}
if self.hasNoTodos == true {
if self.hidePopUp == false {
VStack {
Text("THIS IS MY POPUP!")
Text("No Items Added Yet")
}.frame(width: 300, height: 400)
}
}
}
}
}
}
class AsyncGetTodosNetworkCall: ObservableObject {
#AppStorage(DBUser.userID) var currentUserId: String?
private var REF_USERS = DB_BASE.collection(DBCOLLECTION.appUsers)
#Published var items = [TodoItem]()
func fetchTodos(toDetach: Bool, handler: #escaping (_ noTodos: Bool) -> ()) {
guard let userID = currentUserId else {
handler(true)
return
}
let userDoc = REF_USERS.document(String(userID))
.collection(DBCOLLECTION.todos)
.addSnapshotListener({ (querySnapshot, error) in
guard let documents = querySnapshot?.documents else {
print("No Documents Found")
handler(true)
return
}
self.items = documents.map { document -> TodoItem in
let todoID = document.documentID
let todoName = document.get(ToDo.todoName) as? String ?? ""
let todoCompleted = document.get(Todo.todoCompleted) as? Bool ?? false
return TodoItem(
id: todoID,
todoName: todoName,
todoCompleted: todoCompleted
)
}
handler(false)
})
if toDetach == true {
userDoc.remove()
}
}
}