SwiftUI willSet vs didSet onReceive

SwiftUI_willSet_vs_didSet_Publishers.swift

// Credit: Michael LaRandeau (@mlarandeau)

import SwiftUI
import Combine
import PlaygroundSupport

class ValueProvider: ObservableObject {
    
    private let didSetSubject = CurrentValueSubject<Int, Never>(0)
    
    @Published var value: Int = 0 {
        didSet {
            didSetSubject.send(value)
        }
    }
    
    var didSetPublisher: AnyPublisher<Int, Never> {
        didSetSubject.eraseToAnyPublisher()
    }
    
    func randomize() {
        value = Int.random(in: 0..<1000)
    }
}

struct TestView: View {
    
    @StateObject var valueProvider = ValueProvider()
    @State var incrementor: Int = 0
    
    var body: some View {
        print("## Body")
        return VStack(spacing: 20) {
            Text("\(valueProvider.value)")
                // If you use valueProvider.didSetPublisher here instead of $value, the onReceive closure gets called multiple times.
                .onReceive(valueProvider.$value) {
                    print("## Update Value: \($0)")
                    // If you use the `didSetPublisher` above in onReceive and uncomment the line below, you will trigger an infinite loop
                    // incrementor += 1
                }
            Text("\(incrementor)")
            Button("Change Number") {
                valueProvider.randomize()
            }
        }
    }
}

PlaygroundPage.current.setLiveView(TestView())