协程 scope 内部 withcontext 并且仅 withContext 使用

Question

you can see below two methods, the first one using withContext and coroutineScope and second function using only coroutine Scope. What if it will used only withContext? or only coroutine scope? Why both need to be used?

override suspend fun deleteAllTasks() {
        withContext(ioDispatcher) {
            coroutineScope {
                launch { tasksRemoteDataSource.deleteAllTasks() }
                launch { tasksLocalDataSource.deleteAllTasks() }
            }
        }
    }

override suspend fun deleteTask(taskId: String) {
    coroutineScope {
        launch { tasksRemoteDataSource.deleteTask(taskId) }
        launch { tasksLocalDataSource.deleteTask(taskId) }
    }
}

Answer 1

In that case there is no need for coroutineScope inside withContext , since withContext does this for you already.

There are situations where using coroutineScope inside withContext could be useful.

withContext(ioDispatcher) {
    coroutineScope {
        launch { tasksRemoteDataSource.deleteAllTasks() }
        launch { tasksLocalDataSource.deleteAllTasks() }
    }
    coroutineScope {
        launch { tasksRemoteDataSource.deleteAllTasks() }
        launch { tasksLocalDataSource.deleteAllTasks() }
    }
}

Here the coroutineScope s are use for parallel decomposition and to delineate the set of concurrent tasks.