How to properly wrap method to dis… | Apple Developer Forums

How to properly wrap method to dispatch it on specific queue in Combine?

Consider the following

I have a method that call external library Lib.

Code Block enum Service {
  enum Invocation { 
    static func findBy(id: String) -> Data? { Lib.FindById(id) }
  }
}

Code Block
enum Service {
enum Invocation {
static func findBy(id: String) -> Data? { Lib.FindById(id) }
}
}

Next, I would like to introduce a Future which wrap this call to be compatible with Combine.

Code Block extension Service {
	static func findBy(id: String) -> Future<Data?, Never> {
      .init { promise in promise(Invocation.findBy(id: id)) }
    }
}

Code Block
extension Service {
static func findBy(id: String) -> Future<Data?, Never> {
.init { promise in promise(Invocation.findBy(id: id)) }
}
}

What is a proper ("Combinish") way to dispatch Invocation.findBy on a given thread/queue?

I would like to dispatch this method on background thread, however, it is too expensive if I call it many times.

Also if I have many Combine modifiers , the call to this method is delayed, correct? But I would like to dispatch invocation on different queue/thread as soon as possible.

.subscribe(on: Scheduler) modifier doesn't change the execution queue/thread of body of future Service.findBy.