Ymir: Custom ViewModel Library for Android

Welcome to Ymir! This library provides a flexible and efficient way to manage UI state and actions in your Android applications using a custom implementation of ViewModel. The library is designed to simplify the handling of UI state changes and actions while leveraging the power of Kotlin's coroutines and Flow APIs.

Features
Getting Started
Usage
- Implementing a ViewModel
- Using with Jetpack Compose
Testing
Demo
Contributions and Feedback

Features

State Management: Easily manage UI state and actions.
Jetpack Compose Integration: Seamlessly integrate with Jetpack Compose.
Coroutine Support: Built-in support for Kotlin coroutines for asynchronous operations.

Getting Started

To get started with this library, add the following dependency to your build.gradle:

dependencies {
    implementation 'io.github.lucas-cordeiro.ymir:core:[last-version]'
}

Replace [last-version] with the latest version available on Maven Central.

Usage

Implementing a ViewModel

Create your UiState and UiAction by extending the interfaces provided by the library:

import io.github.lucascordeiro.ymir.core.state.UiState
import io.github.lucascordeiro.ymir.core.action.UiAction

data class HomeUiState(
    val isLoading: Boolean = false
) : UiState

sealed class HomeUiAction : UiAction {
    data class ShowToast(val message: String) : HomeUiAction()
}

Create your ViewModel by extending the custom ViewModel class provided by the library:

import io.github.lucascordeiro.ymir.core.viewmodel.ViewModel

class HomeViewModel() : ViewModel<HomeUiState, HomeUiAction>(HomeUiState()) {
    // ViewModel implementation
}

To update the UiState, you need to call setState:

viewModelScope.launch {
    setState { state -> state.copy(isLoading = true) }
}

To send an UiAction need to call sendAction:

viewModelScope.launch {
    sendAction { MainUiAction.ShowToast("Hello, Android!") }
}

Note: Both setState and sendAction are suspend functions.

Using with Jetpack Compose

In your Jetpack Compose UI, you can easily observe state and handle actions using the provided utility functions. Here's how:

@Composable
fun HomeScreen(viewModel: HomeViewModel) {
    val state by viewModel.state.collectAsStateWithLifecycle()

    ObserveActions(
        viewModel = viewModel,
        handleAction = ::handleAction
    )

    // UI Code using state
}

fun handleAction(action: HomeUiAction) {
    when (action) {
        is HomeUiAction.ShowToast -> {
            // Show toast message
        }
    }
}

Testing

This library includes support for testing ViewModel implementations by providing a utility class, ViewModelObserver, that simplifies the management of UiState and UiAction during tests.

To use the testing utilities provided by the library, add the following dependency to the testImplementation section of your build.gradle:

dependencies {
    testImplementation 'io.github.lucas-cordeiro.ymir:test:[last-version]'
}

Here's an example of how to write tests using the ViewModelObserver:

@get:Rule
val mainDispatcherRule = MainDispatcherRule() // Not included in library

private lateinit var viewModel: HomeViewModel
private val observer by lazy {
    ViewModelObserver(
        viewModel = viewModel,
        testDispatcher = mainDispatcherRule.testDispatcher
    )
}

@Before
fun setup() {
    viewModel = HomeViewModel()
}

@Test
fun someTest() = runTest {
    observer.start()

    val state = observer.state
    val action = observer.action

    // Simulate user interactions, such as button clicks

    advanceUntilIdle()

    // Add asserts to verify the expected outcomes

    observer.stop()
}

Demo

For a demonstration of how to implement and use this library, check out the HomeActivity in the app module of this repository. Additionally, the app module includes a unit test example for the ViewModel, demonstrating how to test UiState and UiAction using the ViewModelObserver.

Contributions and Feedback

As the sole developer of this library, I am open to suggestions, improvements, and feedback to make it even better! If you have any ideas, encounter a bug, or would like to share your thoughts, feel free to open an issue.

Your contributions and feedback are highly appreciated as they help enhance the quality and functionality of this library.

lucas-cordeiro/Ymir