swiftui - Swift UI @ObservedObject not working, found weird behaviour when implementing another protocol

Question

following this guide "Stanford university" I implemented a model(struct) named MemoryGame with a second struct inside named card ( implementing Identifiable ) with viewModel named EmojiMemoryGame(class) witch holds the model(MemoryGame) with a wrapper "@Published". in the contentView I have the viewModel(EmojiMemoryGame) with "@ObservedObject" wrapper.

This works fine, when the data changed the view get notified and updates, But I found 1 problem I don't understand, when the card struct ( the one in MemoryGame struct ) witch implements "Identifiable" implement another protocol ( i tried Equatable and Comparable ) the UI not getting updated ( I checked that the data is changing ). when implementing Equatable with the "func ==" the UI not updating at all, it become weirder when I remove the Equatable name from the struct declaration but I leave the "func ==" in there, its work.

I tried the same with Comparable and implemented the funcs "<" and "==", same thing, the @ObservedObject not working but if I remove the Comparable from the struct declaration its works.

*side question: when I removed Equatable from the struct but left the "==" func inside its still gave me the option to compare both object like it still implements Equatable. is this normal ?

I new to this and still don't know how to debug the objectWillChange.send() ( I tried but so far I failed I think )

the code is below

this is the model MemoryGame, I commented out the protocols that brake the functionality

import Foundation


  struct MemoryGame<CardContent> {

var cards : [Card]



mutating func choose(card : Card) {
    cards[index].isFaceUp = !cards[index].isFaceUp
   
}

struct Card : Identifiable /* , Equatable , Comparable */  {
    //        static func < (lhs: MemoryGame<CardContent>.Card, rhs: MemoryGame<CardContent>.Card) -> Bool {
    //            lhs.id < rhs.id
    //        }
    //
    //        static func == (lhs: MemoryGame<CardContent>.Card, rhs: MemoryGame<CardContent>.Card) -> Bool {
    //            lhs.id == rhs.id
    //        }
    //
    static func == (lhs: Card, rhs: Card) -> Bool {
        return lhs.id == rhs.id
    }
    
    var isFaceUp : Bool = true
    var isMatched : Bool = false
    var content : CardContent
    var id : Int
}

}

this is the viewModel EmojiMemoryGame

import SwiftUI


    class EmojiMemoryGame : ObservableObject {

typealias CoreGame = MemoryGame<String>

@Published private var model : CoreGame = EmojiMemoryGame.createMemoryGame()

func choose(card:CoreGame.Card) {
    model.choose(card: card)
}

}

and this is the contentVIew

import SwiftUI

 struct EmojiMemoryGameView: View {

@ObservedObject var viewModel : EmojiMemoryGame

var body: some View {
    HStack {
        ForEach(viewModel.cards) { card in
            CardView(card: card).onTapGesture {
                self.viewModel.choose(card: card)
            }
        }
    }
    .padding()
    .foregroundColor(.orange)
}
}

 struct CardView : View {

var card : MemoryGame<String>.Card

var body: some View {
    ZStack {
        if card.isFaceUp {
            RoundedRectangle(cornerRadius: 10.0).fill().foregroundColor(.white)
            RoundedRectangle(cornerRadius: 10.0).stroke(lineWidth: 3.0)
            Text(card.content)
                .font(.system(size: 200))
                .minimumScaleFactor(0.1)
                .lineLimit(1)
                
                
        } else {
            RoundedRectangle(cornerRadius: 10.0).fill()
        }
        
    }.aspectRatio(CGSize(width: 20, height: 30), contentMode: .fit)
 }
 }



struct ContentView_Previews: PreviewProvider {
static var previews: some View {
    EmojiMemoryGameView(viewModel: EmojiMemoryGame())
}

}

question from:https://stackoverflow.com/questions/65916694/swift-ui-observedobject-not-working-found-weird-behaviour-when-implementing-an

Answer 1

Waitting for answers