Queues and schedulers

There are built-in scheduler types that work with Grand Central Dispatch (GCD) queues and NSOperationQueues, including SerialDispatchQueueScheduler, which can dispatch work on a specified serial dispatch queue; ConcurrentDispatchQueueScheduler, which will dispatch on a concurrent dispatch queue; and OperationQueueScheduler, which will perform the work on a specifiedNSOperationQueues.

We can also specify our own custom schedulers by conforming to the immediateScheduler protocol.

Scheduler Singletons

There are a couple of Singleton schedulers that we can use for some common needs such as the following:

• CurrentThreadScheduler
• MainScheduler

CurrentThreadScheduler represents the current thread and is the default scheduler. The MainScheduler, on the other hand, represents the main thread and is typically used for all UI-related work.

Specifying a scheduler

To specify a scheduler on which a subscription is created, handler-executed, and disposed of, we use the subscribeOn operator...