Jarosław Michalik👉 one thing you need to understand Clean Architecture

15:25 26.01.2024·1 min read

Hi MailingR

There is really only one thing you need to understand Clean Architecture. And it's The Dependency Rule.

First, what is dependency rule?

The flow of control goes through inner and outer circles.

The outermost layers are more "concrete" while the inner layers are more general and abstract.

Let's suppose that you have code responsible for managing GPS location updates.

We can treat this code as an interface adapter (green layer) for Android device capability.

You define GpsProvider / Service / Controller / however you call it in :location module.

And you create an interface for Gps Provider in domain module.

:location module is dependent on :domain module and is returning domain entities.

Then to access data from this provider, you create use case in :domain module.

Because you operate on abstractions and domain models, the whole pure Kotlin logic can be implemented as regular Kotlin class without any external dependencies.

Now it's time to present this "Orders" data enchanced by GPS data to the UI.

You're creating ViewModel for your Composable or Fragment in :app or :presentation module.

You can treat this layer as an interface adapter (green circle) for frameworks & drivers (UI)

Interface Adapter (:location)-> accessing location data

Interface Adapter (:app or :presentation)-> responsible for UI

Interface Adapter (:data-remote)-> responsible for network requests

Interface Adapter (:data-local) -> responsible for local DB

Control flows through :domain

The same scenario as in :location module applies for:

- data-remote (Retrofit / Ktor)

- data-local (Room, Realm)

Your ViewModel is accessing UseCase, which has repositories / services injected.

Every other module depends on :domain.

:domain is independent.

That's really it.

Domain is the ♥️ of our application. No need to pollute domain with framework dependencies.

If you liked this newsletter issue, I'm sure you'll like also our AndroidPro platform, where we discuss Android and Android related things for developers on any experience levels.

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happy coding,

Jarek