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Reactor

Project Reactor is a functional reactive programming library, consisting of “publishers” and “operations”

Publishers, Fluxes, and Monos

A Publisher is just a higher level interface for both Fluxes and Monos. You can think of them as streams. They are more sophisticated than traditional streams, notably in operating by push and pull, but let’s not worry about that for now.

A Flux is just a Publisher with multiple elements. We will mostly be dealing with these.

A Mono is just a Publisher with one element.

Flux and Mono Creation

Fluxes and Monos can be created with the toFlux() and toMono() kotlin extension functions. More on that here

import reactor.core.publisher.*

val flux1 = listOf("a", "b", "c").toFlux()

Operations

Operations are the functional part of functional reactive programming. Every Publisher has functions that transform it into one or more other publishers.

import reactor.core.publisher.*

val flux1 = listOf("a", "b", "c").toFlux()
val flux2 = flux1.map { "$it$it" } // "aa", "bb", "cc" 

There are many operators. A full list for Fluxes can be found here and for Monos here.