Reactive Programming in Kotlin

Counting emissions (count operator)

The count operator subscribes to a producer, counts the emissions, and emits a Single, containing the count of emissions by the producer.

Here is an example:

    fun main(args: Array<String>) { 
      listOf(1,5,9,7,6,4,3,2,4,6,9).toObservable() 
      .count() 
      .subscribeBy { println("count $it") } 
    } 

The following is the output:

As we can see from the output, this operator counts the emissions from the producer, and emits the count once it receives the onComplete notification.