Ignores elements from the upstream publisher until it receives an element from a second publisher.
- iOS 13.0+Beta
- macOS 10.15+Beta
- Mac Catalyst 13.0+Beta
- tvOS 13.0+Beta
- watchOS 6.0+Beta
- Xcode 11.0+Beta
A publisher to monitor for its first emitted element.
A publisher that drops elements from the upstream publisher until the
other publisher produces a value.
This publisher requests a single value from the upstream publisher, and it ignores (drops) all elements from that publisher until the upstream publisher produces a value. After the
other publisher produces an element, this publisher cancels its subscription to the
other publisher, and allows events from the
upstream publisher to pass through. After this publisher receives a subscription from the upstream publisher, it passes through backpressure requests from downstream to the upstream publisher. If the upstream publisher acts on those requests before the other publisher produces an item, this publisher drops the elements it receives from the upstream publisher.