Is there any pattern in Jetpack Compose to add act...

# compose

[Noé Casas]

Is there any pattern in Jetpack Compose to add actions to the TobAppBar from a Composable that does not have access to it? I am thinking in something like SwiftUI’s toolbar and ToolbarItem (e.g. see https://swiftwithmajid.com/2020/07/15/mastering-toolbars-in-swiftui/) . Also, is there a mechanism or pattern to set the `TopAppBar`’s title from somewhere else, like SwiftUI’s navigationTitle ?

[jim]

add actions to the TobAppBar from a Composable that does not have access to it

As a general rule of thumb, this sentence sounds like an inherent antipattern. Side-effects always look "easy" in quick code snippets, and then when they're all combined together to build a real application then the conglomeration becomes impossible to reason about, which is why we avoid side effects. A widget should not be modifying something it doesn't have access to. If a widget needs access to something (like a data model), that should be passed in explicitly.

[Kari Kähkönen]

I was struggling with something related a couple of weeks ago. In my case I had a Scaffold (with TopAppBar) and bodyContent that contained NavHost from the Navigation component to display the current screen. I had a composable for a screen that was observing data from a ViewModel, but I also wanted to display some text in the app bar based on the state managed by the ViewModel.

I was considering two options:

• Just hide the top app bar in the Scaffold when user navigates to this particular screen and have the app bar as part of the screen composable itself
• Share the ViewModel with the composables for the top app bar and for the screen. I didn't immediately figure out a clean way to share the ViewModel, though.
In the end I didn't need the feature, so I didn't spend much time thinking about it. But I might come back to it in the future.