Intermediate Combine
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When a Subscriber initially calls subscription.request(_:), it specifies the maximum number of values it is willing to receive.
func receive(_ input: Self.Input) -> Subscribers.Demand //ON SLIDE
example(of: "Dynamically adjusting Demand") {
final class IntSubscriber: Subscriber {
typealias Input = Int
typealias Failure = Never
func receive(subscription: Subscription) {
subscription.request(.max(2))
}
func receive(_ input: Int) -> Subscribers.Demand {
print("Received value", input)
switch input {
case 1:
return .max(2) // 1
case 3:
return .max(1) // 2
default:
return .none // 3
}
}
func receive(completion: Subscribers.Completion<Never>) {
print("Received completion", completion)
}
}
let subscriber = IntSubscriber()
let subject = PassthroughSubject<Int, Never>()
subject.subscribe(subscriber)
subject.send(1)
subject.send(2)
subject.send(3)
subject.send(4)
subject.send(5)
subject.send(6)
}