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Architecture

The project is layered traditionally with a View, Presentation, Model separation and presents a MVI inspired from Yusuf Ceylan's architecture but adapted to Compose.

Architecture layers:

• View - Composable screens that consume state, apply effects and delegate events.
• ViewModel - AAC ViewModel that manages and reduces the state of the corresponding screen. Additionally, it intercepts UI events and produces side-effects. The ViewModel lifecycle scope is tied to the corresponding screen composable.
• Model - Repository classes that retrieve data. In a clean architecture context, one should use use-cases that tap into repositories.

There are a three core components described:

• State - data class that holds the state content of the corresponding screen e.g. list of User, loading status etc. The state is exposed as a Compose runtime MutableState object from that perfectly matches the use-case of receiving continuous updates with initial value.

• Event - plain object that is sent through callbacks from the UI to the presentation layer. Events should reflect UI events caused by the user. Event updates are exposed as a MutableSharedFlow type which is similar to StateFlow and that behaves as in the absence of a subscriber, any posted event will be immediately dropped.

• Effect - plain object that signals one-time side-effect actions that should impact the UI e.g. triggering a navigation action, showing a Toast, SnackBar etc. Effects are exposed as ChannelFlow which behave as in each event is delivered to a single subscriber. An attempt to post an event without subscribers will suspend as soon as the channel buffer becomes full, waiting for a subscriber to appear.

Every screen/flow defines its own contract class that states all corresponding core components described above: state content, events and effects.