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Mastering Kotlin Coroutines

Coroutine Builders: Using coroutineScope

Explore how to use coroutineScope as a suspending function to create coroutine scopes within other suspending functions. Understand the importance of coroutineScope for managing concurrency, returning results, and structuring asynchronous code in Kotlin. Gain insights into its role alongside other coroutine builders and scopes to effectively handle asynchronous operations without passing explicit scopes to functions.

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Imagine that in some repository function, we need to asynchronously load two resources—for example, user data and a list of articles. In this case, we want to return only those articles that the user should see. To call async, we need a scope, but we don’t want to pass it to a function. To create a scope out of a suspending function, we use the coroutineScope function.

Kotlin 1.5
suspend fun getArticlesForUser( 
    userToken: String?,
): List<ArticleJson> = coroutineScope {
    val articles = async { articleRepository.getArticles() } 
    val user = userService.getUser(userToken) 
    articles.await()
        .filter { canSeeOnList(user, it) }
        .map { toArticleJson(it) }
}

The suspending function coroutineScope creates a scope for its lambda expression. The function returns whatever the lambda expression ...