removeDuplicates()
Publishes only elements that don’t match the previous element.
Declaration
func removeDuplicates() -> Publishers.RemoveDuplicates<Self>Return Value
A publisher that consumes — rather than publishes — duplicate elements.
Discussion
Use removeDuplicates() to remove repeating elements from an upstream publisher. This operator has a two-element memory: the operator uses the current and previously published elements as the basis for its comparison.
In the example below, removeDuplicates() triggers on the doubled, tripled, and quadrupled occurrences of 1, 3, and 4 respectively. Because the two-element memory considers only the current element and the previous element, the operator prints the final 0 in the example data since its immediate predecessor is 4.
let numbers = [0, 1, 2, 2, 3, 3, 3, 4, 4, 4, 4, 0]
cancellable = numbers.publisher
.removeDuplicates()
.sink { print("\($0)", terminator: " ") }
// Prints: "0 1 2 3 4 0"