Using delegates in Swift - ios

Question

I know that this may be tagged as a repeat question, but the ones that exist have not helped me implement delegates in Swift with SwiftUI. My issue can be see in the code below. I have a View and VM, TodaysVM. In here, I do a network request, that downloads movie data from an API, and saves the data to CoreData. In order to show graphs, the HabitVM needs to fetch the data from CoreData, and then do some long processing on it.
For this, I was looking into a way for one class to send a message notification to another class. So I stumbled onto using delegates (not sure if this is correct?). But essentially the idea would be that the TodayVM refreshes its data (which the user can do a pull to refresh on this page), it also sends a message to HabitsVM to start processing (so the data can be done by the time the user navigates to this page. I am not sure if there is a better way to do this, and I was trying to stay away from a singleton approach, passing one class into class, or creating a new instance of one of the classes.
In the code below, I have the delegates set up but 'print("Data update required!")' is never executed. From my research I understand this to be because I never set a value to the delegate? So the delegate value is nil, and therefore the
delegate?.requireUpdate(status: true)
Is never actually executed. Which makes sense, since delegate is an optional, but never assigned a value. So I was curious how I would assign it a value in SwiftUI? And if using delegates is even the best method to have to separate classes send updateRequired status updates.
import SwiftUI
import Foundation
// protocol
protocol MovieNotifierDelagate: AnyObject {
func requireUpdate(status: Bool)
}
struct HabitView {
#StateObject var habitVM = HabitsVM()
var body: some View {
Text("Hello")
}
}
struct TodaysView {
#StateObject var todayVM = TodayVM()
var body: some View {
Text("Hi!")
}
}
class HabitsVM: ObservableObject, MovieNotifierDelagate {
init() {
}
func requireUpdate(status: Bool) {
print("Data update required!")
reprocessData()
}
func reprocessData() {
print("Processing")
}
}
class TodayVM: ObservableObject {
weak var delegate: MovieNotifierDelagate?
init() {
//Does some network call and downloads data, and saves to CoreData
sendUpdate(status: true)
}
func sendUpdate(status: Bool) {
guard status else {
print ("No update")
return
}
delegate?.requireUpdate(status: true)
}
}
// Controlling Page
struct HomeView: View {
//Default the user to the today view
#State private var selection = 1
var body: some View {
TabView(selection: $selection) {
HabitView()
.tag(0)
.tabItem {
VStack {
Image(systemName: "books.vertical")
Text("Habits")
}
}
TodaysView()
.tag(1)
.tabItem {
VStack {
Image(systemName: "backward.end.alt")
Text("Rewind")
}
}
}
}
}