A publisher that exposes a method for outside callers to publish elements.
- 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 subject is a publisher that you can use to ”inject” values into a stream, by calling its
send() method. This can be useful for adapting existing imperative code to the Combine model.