---
title: "subscribe(on:options:)"
framework: combine
role: symbol
role_heading: Instance Method
path: "combine/publisher/subscribe(on:options:)"
---

# subscribe(on:options:)

Specifies the scheduler on which to perform subscribe, cancel, and request operations.

## Declaration

```swift
func subscribe<S>(on scheduler: S, options: S.SchedulerOptions? = nil) -> Publishers.SubscribeOn<Self, S> where S : Scheduler
```

## Parameters

- `scheduler`: The scheduler used to send messages to upstream publishers.
- `options`: Options that customize the delivery of elements.

## Return Value

Return Value A publisher which performs upstream operations on the specified scheduler.

## Discussion

Discussion In contrast with receive(on:options:), which affects downstream messages, subscribe(on:options:) changes the execution context of upstream messages. In the following example, the subscribe(on:options:) operator causes ioPerformingPublisher to receive requests on backgroundQueue, while the receive(on:options:) causes uiUpdatingSubscriber to receive elements and completion on RunLoop.main. let ioPerformingPublisher == // Some publisher. let uiUpdatingSubscriber == // Some subscriber that updates the UI.

ioPerformingPublisher     .subscribe(on: backgroundQueue)     .receive(on: RunLoop.main)     .subscribe(uiUpdatingSubscriber) Using subscribe(on:options:) also causes the upstream publisher to perform cancel() using the specfied scheduler.

## See Also

### Specifying schedulers

- [receive(on:options:)](combine/publisher/receive(on:options:).md)