How to update SwiftUI Binding variable in another CLASS - swiftui

Question

I am a newbie to SwiftUI, and I have a simple question, how to update the #State content of a VIEW in another Class, a simulated Code is as follows
When I press the button, the fruits.price variable is not updated in the View. Is there something I'm missing, or is there something wrong I don't understand
class Fruits: ObservableObject {
#Published var price = 1
}
struct ContentView: View {
#ObservedObject var fruits = Fruits()
var extenalClass = ExtenalClass()
var body: some View {
VStack {
Text(String(fruits.price))
.padding()
Button("Add-Me") {
// fruits.price += 1
extenalClass.fChangePrice()
print (fruits.price)
}
}
}
}
class ExtenalClass: ObservableObject {
#ObservedObject var fruits = Fruits()
func fChangePrice() {
fruits.price = 888
print (fruits.price)
}
}

Answer 1

We don't use classes in SwiftUI for model types, we use structs. Any change to the struct is detected by SwiftUI as a change to the state, so body is called to get the new Views, e.g.
struct Fruit {
var price = 1
}
struct ContentView: View {
#State var fruit = Fruit()
var body: some View {
VStack {
Text(fruit.price, format: .currency)
.padding()
Button("Add-Me") {
fruit.price += 1
print (fruit.price)
}
}
}
}

Answer 2

Thanks jnpdx, Baglan for the guidance .... I just found out my answer (probably not the right way), which is to put #Published and "My Function" together in the same CLASS...that is, Function is placed in the CLASS containing #Published...or, another way of saying , put #Published in the CLASS that contains "My Function"
class Fruits: ObservableObject {
#Published var price = 1
// Move (ExtenalClass) Function to here
func fChangePrice() {
price = 888
print (price)
}
}
struct ContentView: View {
#ObservedObject var fruits = Fruits()
// var extenalClass = ExtenalClass()
var body: some View {
VStack {
Text(String(fruits.price))
.padding()
Button("Add-Me") {
// fruits.price += 1
fruits.fChangePrice() // Modified
print (fruits.price)
}
}
}
}
//class ExtenalClass: ObservableObject {
// #ObservedObject var fruits = Fruits()
// func fChangePrice() {
// fruits.price = 888
// print (fruits.price)
// }
//}