Scheduler Behavior
Understand the behavior of subscribeOn and observeOn operators in RxJava and how they control threading in reactive programming. Learn the significance of where to place these operators in an observable chain to manage concurrency effectively. This lesson explains why only the first subscribeOn call affects the stream, how observeOn can switch threads multiple times, and provides practical advice for optimal thread management in your reactive code.
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As we can see, using .subscribeOn() and .observeOn() makes threading easy, but there are some intricacies to these operators that need to be discussed.
.subscribeOn()
As pointed out earlier, it doesn’t matter where the .subscribeOn() call appears in the operator chain. However, it’s important to note that only the first .subscribeOn() call is applied. Any subsequent .subscribeOn() calls will have no effect. Oftentimes, Observable objects are created as part of a library or API and provided to a client via an interface. This interface documentation should clearly state if the returned Observable will have already been relegated to some Scheduler via .subscribeOn() because, if it has, the client will no longer be able to make its own .subscribeOn() call.
Remember: Only the first ...