prepend(_:)
Prefixes a publisher’s output with the specified values.
Declaration
func prepend(_ elements: Self.Output...) -> Publishers.Concatenate<Publishers.Sequence<[Self.Output], Self.Failure>, Self>Parameters
- elements:
The elements to publish before this publisher’s elements.
Return Value
A publisher that prefixes the specified elements prior to this publisher’s elements.
Discussion
Use prepend(_:) when you need to prepend specific elements before the output of a publisher.
In the example below, the prepend(_:) operator publishes the provided elements before republishing all elements from dataElements:
let dataElements = (0...10)
cancellable = dataElements.publisher
.prepend(0, 1, 255)
.sink { print("\($0)", terminator: " ") }
// Prints: "0 1 255 0 1 2 3 4 5 6 7 8 9 10"