Programming Clojure, 2nd Edition

Use Atoms for Uncoordinated, Synchronous Updates

Atoms are a lighter-weight mechanism than refs. Where multiple ref updates can be coordinated in a transaction, atoms allow updates of a single value, uncoordinated with anything else.

You create atoms with atom, which has a signature very similar to ref:

(atom initial-state options?)
; options include:
;   :validator validate-fn
;   :meta metadata-map

Returning to our music player example, you could store the current-track in an atom instead of a ref:

(def current-track (atom "Venus, the Bringer of Peace"))
-> #'user/current-track

You can dereference an atom to get its value, just as you would a ref:

(deref current-track)
-> "Venus, the Bringer of Peace"

@current-track ...