Transforms all elements from the upstream publisher with a provided closure.
- 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 closure that takes one element as its parameter and returns a new element.
A publisher that uses the provided closure to map elements from the upstream publisher to new elements that it then publishes.