Open Radar

 
When onReceive is used within the body of a ViewModifier, it is not called. I've found a workaround: If I call onAppear (with no arguments) prior to calling onRecieve, it works! (Even though onAppear is documented to have no affect when called with no argument—though I'm unsure why that's an option then.)

struct BrokenModifier: ViewModifier {
    func body(content: Content) -> some View {
        content
            .onReceive(Timer.publish(every: 1, on: .main, in: .default).autoconnect()) { _ in
                print("This will never print!")
        }
    }
}

// Learned workaround from StackOverflow: https://stackoverflow.com/questions/61190398/swiftui-viewmodifier-doesnt-listen-to-onreceive-events
struct WorkaroundModifier: ViewModifier {
    func body(content: Content) -> some View {
        content
            .onAppear()
            .onReceive(Timer.publish(every: 1, on: .main, in: .default).autoconnect()) { _ in
                print("This will print, thanks to the supposed no-op onAppear.")
        }
    }
}


Expected: BrokenModifier, when used, should print every 1 second, just like WorkaroundModifier.
Actual: BrokenModifier, when used, never invokes the onReceive closure argument