clojure.core/atom

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Type: function Added: Clojure 1.0 Examples: 5 Runnable: 2

([x] [x & options])

Creates and returns an Atom with an initial value of x and zero or more options (in any order):

:meta metadata-map

:validator validate-fn

If metadata-map is supplied, it will become the metadata on the atom. validate-fn must be nil or a side-effect-free fn of one argument, which will be passed the intended new state on any state change. If the new state is unacceptable, the validate-fn should return false or throw an exception.

Examples

by devn on 2010-08-10 . May have evaluation errors. ▶

(def my-atom (atom 0)) #'user/my-atom @my-atom 0 (swap! my-atom inc) 1 @my-atom 1 (swap! my-atom (fn [n] (* (+ n n) 2))) 4 (reset! my-atom 0) 0 @my-atom 0

by mzenzie on 2015-06-04 . May have evaluation errors. ▶

(def a (atom #{})) #'user/a (swap! a conj :tag) #{:tag} @a #{:tag}

by bostonaholic on 2015-12-23 . May have evaluation errors. ▶

(def my-atom (atom 0 :validator even?)) #'user/my-atom @my-atom 0 (swap! my-atom inc) IllegalStateException Invalid reference state clojure.lang.ARef.validate (ARef.java:33) (swap! my-atom (partial + 2)) 2 @my-atom 2

by ibercode on 2018-02-13 ▶

(def car (atom {:make "Audi" :model "Q3"})) @car ;;{:make "Audi", :model "Q3"} (swap! car assoc :model "Q5") ;;{:make "Audi", :model "Q5"} (reset! car {:make "" :model ""}) ;;{:make "", :model ""}

by djblue on 2022-08-26 ▶

(defn atom? [v] #?(:clj (instance? clojure.lang.Atom v) :cljs (satisfies? cljs.core/IAtom v))) (atom? (atom nil)) ;; => true

See also

• clojure.core/reset!
• clojure.core/swap! (6)
• clojure.core/compare-and-set! (1)
• clojure.core/add-watch (3)
• clojure.core/remove-watch
• clojure.core/set-validator! (0)
• clojure.core/swap-vals!
• clojure.core/reset-vals!
• clojure.core/ref-set

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