Just a general question about MVVM: Where to put code for IO Operations? I know you shouldn’t put bu...

# android

[Aaron Waller]

Just a general question about MVVM:
Where to put code for IO Operations?
I know you shouldn’t put business logic in the UI layer but also no context in the VIewModel.
So where to put for example a function to download a file to internal storage? I need the context for that and it also has nothing to do with UI.

[ildar.i [Android]]

In repository. You launch bg operation from vm and in the bg your repository works with files, network etc

[Aaron Waller]

But how do I get the context in my repository?

[Aaron Waller]

From my UI layer (Button click) I call the viewModel which calls the repository and there I write the Code to save the file? So I still have to pass the context all the way through the viewmodel?

[ildar.i [Android]]

usually you would inject context in repository. or better contentResolver

[lam bui]

Create function VM fun (pass prams context) -> call from UI layer( in this have context)

[Ronald Wolvers]

I've found Hilt to work really nicely for this. If you annotate your VM with @HiltViewModel you can inject any class that talks to a DB or does networking in a really convenient way (using @Inject) and then from your VM you can launch a coroutine that is scoped to your VM's lifecycle using viewModelScope.launch { and then call back to your UI with a LiveData. (https://developer.android.com/training/dependency-injection/hilt-android)

[Ronald Wolvers]

Context in any Hilt object is obtained with @ApplicationContext

[Patrick Kellison]

If you have an Application object, you could use that as well