Specifies the scheduler on which to perform subscribe, cancel, and request operations.
SDKs
- iOS 13.0+
- macOS 10.15+
- Mac Catalyst 13.0+
- tvOS 13.0+
- watchOS 6.0+
- Xcode 11.0+
Framework
- Combine
Declaration
func subscribe<S>(on scheduler: S, options: S.SchedulerOptions? = nil) -> Publishers.SubscribeParameters
schedulerThe scheduler on which to receive upstream messages.
optionsOptions that customize the delivery of elements.
Return Value
A publisher which performs upstream operations on the specified scheduler.
Discussion
In contrast with receive(on:, which affects downstream messages, subscribe(on:) changes the execution context of upstream messages. In the following example, io uses background to process requests. However, it uses Run to send elements to the subscriber.
let ioPerformingPublisher == // Some publisher.
let uiUpdatingSubscriber == // Some subscriber that updates the UI.
ioPerformingPublisher
.subscribe(on: backgroundQueue)
.receiveOn(on: RunLoop.main)
.subscribe(uiUpdatingSubscriber)