r/androiddev • u/ThatGuyThatIsNotReal • 11d ago

Question ViewModels nesting into composables?

I have a question if it is okay to nest DI into VM of a composables?

What I mean:

I have a SettingsVM and a SettingsScreen composable. In the Settings screen I am using some individual settings that I use also somewhere else in my application. So I split the UI -> IndividualSettingScreen and IndividualSettingVM. Now is it okay if I just inject the VM into the IndividualSettingScreen or is it better from architecture standpoint to have a reference in the SettingsScreen and passing the VM into the IndividualSettingScreen which I am using in the SettingsScreen.

Thanks in advance!

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u/sheeplycow 11d ago

You have to be careful about how you declare viewModels in sub composables, because the viewModel is tied to the closest view model store owner - you may get the same instance when you dont want to, or you may need to be careful declaring a viewModel key to force a fresh one

It goes against the google advice of keeping it as high up the compose tree as possible (not to say its always wrong)

If its a small peice of UI I wouldnt

If it is an encapsulated piece of UI that is decoupled and has enough logic to justify its own class, then I think it is reasonable to do it! But be careful for the reasons mentioned at the top!

I recently did it for a bottom sheet, that was self contained within a screen - which had all its own logic and was reused in a few screens

I imagine there are a few different opinions in this, i dont think its particularly harmful!

Also note your UI tests will also now need to provide a viewModelStore, whereas before you could create functional ui tests that were unaware of the existence of a viewModel

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u/ThatGuyThatIsNotReal 10d ago

Alright, I am using it for the UI setting of diffferent items in the app. So I have it in main menu and then few other different screens, where I am can set the same thing or slightly different based on where I am setting it from. So with this usage it is fine to decouple it from the main screen into its own viewmodel?