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Overview.md

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OVERVIEW

Modularization

The stratergy followed for Modularizing the application is heavily inspired from nowinandroid
and ivywallet and also keeping loose coupling in mind

Modules

The app consists of the following modules.

Name Responsibilities Key classes and dependencies
app Top level module that combines the whole application's modules.Defines all the composable screens and sets up the navigation App, MainActivity
mainly depends on navigation module navigation
navigation Responsible for handling navigation events through out the whole application .
Also defines Destinations 		contains Navigator and NavHost navcontroller
Home Contains Home Screen and uses core:Network to fetch images from network
 Mainly depends oncore:Network core:Persistence
Favourites Contains Favourites Screen and is responsible for fetching images from database
 Depends on core:Persistence
Core:Domain Contains all the top level abstract declarations used through out the application
Also includes data models 		contains FlowAction SharedFlowAction FlowViewMoel
Core:Network Handles logic for fetching data from the network using ktor for Http request and exposing
that as Action for other modules to use 		ImageDto NetworkFlowAction
Core:Persistence Handles logic related to persistence and exposes the functionality
as Actions for other modules to use 		coreDbImageDao ImageEntity

Architecture

The architecture is primarily MVVM + Functional Reactive programming paradigm

The UI paradigm is an endless cycle of states and events: State -> Event -> State' -> Event' -> State'' -> ….

  • A UIState made of primitives depicts the state of the screen at a particular instant
  • A UIEvent depicting all possible events originating from the screens
  • FlowViewModel producing a Flow of UI states and receiving a Flow events.
  • @Composable Screens that transforms UiState to Ui and emitting UIEvents

This way we ensure our Ui is reactive and always has the latest UiState

Actions

Actions refers to Functions that have side-effects . For example, sending HTTP requests or querying a database. These are alternate to repositories in typical MVVM approach or use cases in Clean Architecture.

Actions basically are closely related to the concept of "signals" or "events" in FRP (Functional Reactive Programming). In FRP, signals are used to represent data streams that can be transformed and combined in various ways to produce new signals.

Similarly, Actions in MVVM+FRP are functions that represent a stream of data that can be transformed and combined to produce new streams of data. Actions are typically used to represent domain logic such as network requests or database queries, and can be composed together to build more complex functionality.

Few Actions defined so far in the application ImagesFlow SaveImageAction