todo-mvp-kotlin-coroutines

This version of the app is called todo-mvp-kotlin-coroutines and is based on todo-mvp-kotlin. The sample aims to:

Replace all asynchronous operations with coroutines, which simplify asynchronous programming by providing possibility to write code in direct style (sequentially).

What you need

Before exploring this sample, you should familiarize yourself with the following topics:

Dependencies

kotlin stdlib
kotlin-android plugin
kotlinx-coroutines-core
kotlinx-coroutines-android

Implementing the app

All functions in TasksDataSource replaces with suspend functions.

interface TasksDataSource {
    suspend fun getTasks(): Result<List<Task>>
    suspend fun getTask(taskId: String): Result<Task>
    suspend fun saveTask(task: Task)
    suspend fun completeTask(task: Task)
    suspend fun completeTask(taskId: String)
    suspend fun activateTask(task: Task)
    suspend fun activateTask(taskId: String)
    suspend fun clearCompletedTasks()
    suspend fun refreshTasks()
    suspend fun deleteAllTasks()
    suspend fun deleteTask(taskId: String)
}

In todo-mvp-kotlin sample functions getTasks and getTask had callbacks with onTasksLoaded and onDataNotAvailable functions. In todo-mvp-kotlin-coroutines sample this functions now return Result which can be ether a Success or Error.

sealed class Result<out T : Any> {
    class Success<out T : Any>(val data: T) : Result<T>()
    class Error(val exception: Throwable) : Result<Nothing>()
}

Testability

To launch coroutines you need to specify a CoroutineContext. In tests all coroutines are launched via runBlocking or with EmptyCoroutineContext.

@Test
fun loadStatisticsWhenTasksAreUnavailable_CallErrorToDisplay() = runBlocking {
    // Tasks data isn't available
    setTasksNotAvailable(tasksRepository)

    // When statistics are loaded
    statisticsPresenter.start()

    // Then an error message is shown
    verify(statisticsView).showLoadingStatisticsError()
}

Code metrics

Files were converted mostly 1:1 from TODO-MVP's Java code.