SwiftUI View not updating when Published variable is changed - ios

Question

On a button press, I my app is trying to contact an api to receive data. This data is then stored in a published variable inside an observable object. For some reason, the view doesn't populate with the data until the button that opens that view is press more than once. I am looking for the view to update with the information received from the api call on the first button press. The code I am referencing is provided below:
DataFetcher.swift:
class DataFetcher: ObservableObject{
#Published var dataHasLoaded: Bool = false
#Published var attendeesLoaded: Bool = false
#Published var useresUventsLoaded: Bool = false
#Published var profilesLoaded: Bool = false
#Published var eventsUpdated: Bool = false
#Published var events: [eventdata] = []
#Published var createdEvents: [eventdata] = []
#Published var profile: profiledata?
#Published var atendees: [atendeedata] = []
#Published var IAmAtending: [atendeedata] = []
#Published var eventNames: [eventdata] = []
#Published var profileList: [profiledata] = []
#Published var token: String = UserDefaults.standard.string(forKey: "Token") ?? ""
private var id: Int = 0
func fetchProfile(id: Int){
// events.removeAll()
profileUrl.append("/\(id)")
self.id = id
let url = URL(string: profileUrl)!
var request = URLRequest(url: url)
if let range = profileUrl.range(of: "/\(id)") {
profileUrl.removeSubrange(range)
}
request.httpMethod = "GET"
print(self.token)
request.addValue("Token \(self.token)", forHTTPHeaderField: "Authorization")
let task = URLSession.shared.dataTask(with: request, completionHandler: parseFetchProfileObject)
task.resume()
}
func parseFetchProfileObject(data: Data?, urlResponse: URLResponse?, error: Error?){
guard error == nil else {
print("\(error!)")
return
}
guard let content = data else{
print("No data")
return
}
if let decodedResponse = try? JSONDecoder().decode(profiledata?.self, from: content) {
DispatchQueue.main.async {
self.profile = decodedResponse
self.profileList.append(self.profile!)
}
}
}
func fetchAtendees(id: Int){
// events.removeAll()
atendeeUrl.append("/\(id)")
print(atendeeUrl)
let url = URL(string: atendeeUrl)!
var request = URLRequest(url: url)
if let range = atendeeUrl.range(of:"/\(id)") {
atendeeUrl.removeSubrange(range)
}
request.httpMethod = "GET"
print(self.token)
request.addValue("Token \(self.token)", forHTTPHeaderField: "Authorization")
let task = URLSession.shared.dataTask(with: request, completionHandler: parseFetchAttendeesObject)
task.resume()
}
EventsUserCreatedView.swift
import Foundation
import SwiftUI
import Mapbox
struct EventsUserCreatedView: View {
#Binding var token: String
#State private var pressedEvent: Bool = false
#State private var selectedEvent: Int = 0
#State private var atendees: [atendeedata] = []
#State private var profileList: [profiledata] = []
#State private var showDeleteEventView: Bool = false
var data: DataFetcher
var mapStyle: URL
var body: some View {
ZStack{
//NavigationView {
if self.mapStyle == MGLStyle.darkStyleURL {
List{
ForEach(self.data.createdEvents){ row in
HStack {
Button("\((row.poi)!)") {
print("Display event information")
self.selectedEvent = row.id
self.pressedEvent = true
}
Spacer()
Button("Delete") {
self.showDeleteEventView = true
print("Deletes the event in this row")
}.buttonStyle(BorderlessButtonStyle())
.padding(4)
.background(Color.red)
.cornerRadius(5)
}.foregroundColor(Color.white)
}
}.background(Color.init(red: 0.05, green: 0.05, blue: 0.05))
//if you hit more buttons than there is room for, it'll be scrollable. make some kind of for loop that iterates over events a user is going to and displays it
// }.navigationBarTitle("My Events")
// .navigationViewStyle(StackNavigationViewStyle())
if pressedEvent{
Group{
if self.data.profilesLoaded == true{
//NavigationView {
List{
ForEach(self.data.profileList){ row in
HStack {
Text("\(row.name)")
.foregroundColor(Color.purple)
Spacer()
}
}
}.background(Color.init(red: 0.05, green: 0.05, blue: 0.05))
//if you hit more buttons than there is room for, it'll be scrollable. make some kind of for loop that iterates over events a user is going to and displays it
//}
} else{
Spacer()
Text("Loading Attendees")
Spacer()
}
}.onAppear{
//this can't be done on appear as it won't update when a different
self.data.profileList = []
self.data.atendees = []
DispatchQueue.main.async{
self.data.fetchAtendees(id: self.selectedEvent)
if self.data.profilesLoaded{
self.profileList = self.data.profileList
self.atendees = self.data.atendees
}
}
}
//.navigationBarTitle("My Attendees")
//.navigationViewStyle(StackNavigationViewStyle())
}
NOTE: datafetcher (the observableobject) is passed to eventsusercreated view by the contentview
any help on how to update my view properly is much appreciated

Answer 1

You've to declare the data as an #ObservedObject.
struct EventsUserCreatedView: View {
//...
#ObservedObject var data = DataFetcher()
//...
}
If you're passing DataFetcher instance as environment object declare it as #EnvironmentObject.
struct EventsUserCreatedView: View {
//...
#EnvironmentObject var data: DataFetcher
//...
}