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# android-architecture

[Slackbot]

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[Javier]

you can use usecases whenever you want if it is in an external layer in clean arch

[dewildte]

I think UseCases are designed to operate as a vertical slice through all the layers.
They encapsulate a business process that involves anywhere from the UI layer al the way down to the entity layer.

[dewildte]

@huthefa Sorry, I do not understand exactly what you are trying to communicate.
Are you asking a question?

[curioustechizen]

I did this in a side project. The situation was a notification listener implemented in the data layer - which needed access to some logic that is also used by the presentation layer. I put the shared logic in a UseCase and it worked fine.

[curioustechizen]

Typical examples of UseCases for mobile app architectures show it being called from a UI logic class like a ViewModel or a Presenter, so one might assume that a UseCase should only exist to serve the UI. In many cases this might be true - you run the UseCase in the scope of the Presenter that calls it.

However there are many situations where it makes sense to call a UseCase from the data layer too - like I mentioned in my example above.

[curioustechizen]

Another example might be calling a UseCase from your code that runs from WorkManager (periodic sync, stuff like that).

[curioustechizen]

Also, I'm guessing people also use a similar architecture in non-UI apps like a backend server, and I'm guessing they might be employing UseCases even for non-end-user actions.

For example, if you have a backend that server the API for your app, it might be employing use-cases to serve a single API request; but it might also be employing UseCases to do periodic work not related to an API request.