SwiftUI mutating func weirdness

[tera]

@luca_bernardi

I would also note that despite the compiler allowing it to do it, SwiftUI really don't expect you creating side effect or doing mutation in your body . The framework can call body at any time and you should not rely on it being called to trigger specific mutation or effects.

"at any time" needs clarification, otherwise it's not obvious when it would be possible to mutate model at all:

var body: some View {
	Text(model.text) // i shall not mutate model here, now that i know it
	Button(...) { // button action
		(1) but can i mutate model here? (1)
		DispatchQueue.main.async {
			(2) or i mutate model here?
		}
	}
	Text(model.something that might depend on (1))
}

...
some async event (e.g. network or timer, etc) -- 
is it safe to mutate model there? or are there any rules 
when it is ok and when it is not? e.g. is timer dispatched 
on main loop guaranteed to run outside of any "body" call?

@luca_bernardi

With the current sample code unfortunately it's hard to provide any suggestion on how would be better to architect this. If you think there is some general functionality that SwiftUI should provide to help solve your use case I would encourage you to file a feedback.

ideally SwiftUI + Swift shall prohibit me doing the wrong thing... if that's possible. with "mutating" method above i'm getting runtime error, but sometimes not even this. ideally that needs to be a compilation error:

var body: some View {
	Text(model.mutatingGetText) // compilation error: can't do that
	Button(...) { // button action
		model.mutatingMethod1() // (1) ok (right?)
		DispatchQueue.main.async {
			model.mutatingMethod1() // (2) ok (right?)
		}
		Text(model.something that might depend on (1))
	}
}