Mastering Kotlin Coroutines/

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Constructing a Coroutine Scope

Constructing a Coroutine Scope

A summary of constructing a coroutine scope and how to write code on Android.

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In previous lessons, we’ve learned about the tools needed to construct a proper scope. It’s time to summarize this knowledge and see how we can use it. We’ll look at two common examples: one for Android, and one for back-end development.

CoroutineScope factory function

The CoroutineScope interface has a single property, coroutineContext.

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interface CoroutineScope {
    val coroutineContext: CoroutineContext
}

Therefore, we can make a class implement this interface and directly call coroutine builders in it.

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class SomeClass : CoroutineScope {
    override val coroutineContext: CoroutineContext = Job()
    fun onStart() { 
        launch {
            // ...
        }
    }
}

However, this approach is not very popular. On the one hand, it’s convenient; on the other, it’s problematic that in such a class, we can directly call other CoroutineScope methods like cancel or ensureActive. Even accidentally, someone might cancel the whole scope, and coroutines won’t start anymore. Instead, we generally prefer to hold a coroutine scope as an object in a property and use it to call coroutine ...