max(18), meaning, Subscriber wanted 10, then it wanted 10 more, but it has only received 2.Īlternate interpretations seem to be that the return from receive is additive to the running total. max(10), and the Publisher gets one more element, and messages the Subscriber with that one element, the return will then be. If for some reason the Subscriber decides to send in another request for. I have seen various interpretations on how these numbers relate, and I of course have my own that I'll postulate here.Ī Publisher has a one element, and it gets a 'request(.max(10))' When it sends that to the Subscriber, and the return demand should be '.max(9)', a reminder to the Publisher (actually a Subscription created by the Publisher) that its expecting 9 more elements. 'A Subscribers.Demand instance indicating how many more elements the subscriber expects to receive.' When a Subscriber receives data, it returns another demand, which the Apple docs state is: Home node Please clarify: how different configurations are handled Do all configurations need own label That will lead to tens of thousands of labels. Matt Gallagher supposes in his excellent 22 Combine Tests article that each of these demands should be additive, and when the Subscription sends elements to the Subscriber, it decrements the count.Ģ) func receive(_ input: Self.Input) -> Subscribers. 'Tells a publisher that it may send more values to the subscriber.' Subscriptions provide this function, and as the Apple Docs say:

The below ignores infinite demand.ġ) func request(_ demand: Subscribers. Combine has two related functions that support 'demand', where Subscribers inform Publishers on the desired number of elements passed to them in a 'receive' function.