Mastering Kotlin Coroutines/

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Coroutine Scope Functions

Coroutine Scope Functions

Learn about the coroutine scope function.

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Imagine that we need to concurrently get data from two (or more) endpoints in a suspending function. Before we explore how to do this correctly, let’s see some suboptimal approaches.

Approaches used before coroutine scope functions

The first approach is calling suspending functions from a suspending function. The problem with this solution is that it’s not concurrent (for example, if getting data from each endpoint takes one second, a function will take two seconds instead of one).

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// Data loaded sequentially, not simultaneously
suspend fun getUserProfile(): UserProfileData {
    val user = getUserData() // (1 sec)
    val notifications = getNotifications() // (1 sec)
    return UserProfileData( 
      user = user,
      notifications = notifications,
   )
}

The easiest way to make two suspending calls concurrently is by wrapping them with async. However, async requires a scope, and using GlobalScope is not a good idea.

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//DOING THIS IS NOT RECOMMENDED AT ALL
suspend fun getUserProfile(): UserProfileData { 
    val user = GlobalScope.async { getUserData() } 
    val notifications = GlobalScope.async {
       getNotifications()
    }
    return UserProfileData(
        user = user.await(), // (1 sec)
        notifications = notifications.await(),
    ) 
}

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