reagi's Introduction

Reagi

Reagi is an FRP library for Clojure and ClojureScript, built on top of core.async.

Installation

Add the following dependency to your project.clj file:

[reagi "0.7.0"]

Overview

Reagi introduces two new reference types: behaviors and event streams.

user=> (require '[reagi.core :as r])
nil

A behavior models continuous change, and is evaluated each time you dereference it.

user=> (def t (r/behavior (System/currentTimeMillis)))
#'user/t
user=> @t
1380475144266
user=> @t
1380475175587

An event stream models a series of discrete changes. Events must be expicitly pushed onto the stream. Dereferencing the event stream returns the last value pushed onto the stream.

user=> (def e (r/events))
#'user/e
user=> (r/push! e 1)
#<Events@66d278af: 1>
user=> @e
1

If the event stream is empty, dereferencing it will block the running thread, much like a promise.

Reagi provides a number of functions for transforming event streams, which mimic many of the standard Clojure functions for dealing with seqs:

user=> (def incremented (r/map inc e))
#'user/m
user=> (r/push! e 2)
#<Events@66d278af: 2>
user=> @incremented
3

Finally, behaviors can be converted to event streams by sampling them at a specified interval:

user=> (def et (r/sample 1000 t))
#'user/et
user=> @et
1380475969885

Documentation

API Docs

Differences in ClojureScript version

The ClojureScript version of Reagi has two main differences from the Clojure version:

Trying to deref an unrealized stream blocks the current thread in Clojure, but raises an error in ClojureScript.
Event streams that fall out of scope in Clojure are automatically cleaned up. In ClojureScript, the reagi.core/dispose function must be manually called on streams before they fall out of scope.