diff options
Diffstat (limited to 'docs/topics/coroutine-context-and-dispatchers.md')
| -rw-r--r-- | docs/topics/coroutine-context-and-dispatchers.md | 30 |
1 files changed, 17 insertions, 13 deletions
diff --git a/docs/topics/coroutine-context-and-dispatchers.md b/docs/topics/coroutine-context-and-dispatchers.md index 9aae1a7a..c35de0e0 100644 --- a/docs/topics/coroutine-context-and-dispatchers.md +++ b/docs/topics/coroutine-context-and-dispatchers.md @@ -65,9 +65,8 @@ context of the main `runBlocking` coroutine which runs in the `main` thread. [Dispatchers.Unconfined] is a special dispatcher that also appears to run in the `main` thread, but it is, in fact, a different mechanism that is explained later. -The default dispatcher that is used when coroutines are launched in [GlobalScope] -is represented by [Dispatchers.Default] and uses a shared background pool of threads, -so `launch(Dispatchers.Default) { ... }` uses the same dispatcher as `GlobalScope.launch { ... }`. +The default dispatcher that is used when no other dispatcher is explicitly specified in the scope. +It is represented by [Dispatchers.Default] and uses a shared background pool of threads. [newSingleThreadContext] creates a thread for the coroutine to run. A dedicated thread is a very expensive resource. @@ -303,8 +302,14 @@ the [Job] of the new coroutine becomes a _child_ of the parent coroutine's job. When the parent coroutine is cancelled, all its children are recursively cancelled, too. -However, when [GlobalScope] is used to launch a coroutine, there is no parent for the job of the new coroutine. -It is therefore not tied to the scope it was launched from and operates independently. +However, this parent-child relation can be explicitly overriden in one of two ways: + +1. When a different scope is explicitly specified when launching a coroutine (for example, `GlobalScope.launch`), + then it does not inherit a `Job` from the parent scope. +2. When a different `Job` object is passed as the context for the new coroutine (as show in the example below), + then it overrides the `Job` of the parent scope. + +In both cases, the launched coroutine is not tied to the scope it was launched from and operates independently. ```kotlin import kotlinx.coroutines.* @@ -313,9 +318,9 @@ fun main() = runBlocking<Unit> { //sampleStart // launch a coroutine to process some kind of incoming request val request = launch { - // it spawns two other jobs, one with GlobalScope - GlobalScope.launch { - println("job1: I run in GlobalScope and execute independently!") + // it spawns two other jobs + launch(Job()) { + println("job1: I run in my own Job and execute independently!") delay(1000) println("job1: I am not affected by cancellation of the request") } @@ -343,7 +348,7 @@ fun main() = runBlocking<Unit> { The output of this code is: ```text -job1: I run in GlobalScope and execute independently! +job1: I run in my own Job and execute independently! job2: I am a child of the request coroutine job1: I am not affected by cancellation of the request main: Who has survived request cancellation? @@ -659,7 +664,6 @@ that should be implemented. [async]: https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/async.html [CoroutineScope]: https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/-coroutine-scope/index.html [Dispatchers.Unconfined]: https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/-dispatchers/-unconfined.html -[GlobalScope]: https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/-global-scope/index.html [Dispatchers.Default]: https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/-dispatchers/-default.html [newSingleThreadContext]: https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/new-single-thread-context.html [ExecutorCoroutineDispatcher.close]: https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/-executor-coroutine-dispatcher/close.html @@ -674,8 +678,8 @@ that should be implemented. [CoroutineScope()]: https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/-coroutine-scope.html [MainScope()]: https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/-main-scope.html [Dispatchers.Main]: https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/-dispatchers/-main.html -[asContextElement]: https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/java.lang.-thread-local/as-context-element.html -[ensurePresent]: https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/java.lang.-thread-local/ensure-present.html +[asContextElement]: https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/as-context-element.html +[ensurePresent]: https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/ensure-present.html [ThreadContextElement]: https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/-thread-context-element/index.html -<!--- END -->
\ No newline at end of file +<!--- END --> |