atom
- (atom x)
- (atom 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.
© Rich Hickey. All rights reserved. Eclipse Public License 1.0
5 Examples
user=> (def my-atom (atom 0)) #'user/my-atom user=> @my-atom 0 user=> (swap! my-atom inc) 1 user=> @my-atom 1 user=> (swap! my-atom (fn [n] (* (+ n n) 2))) 4 user=> (reset! my-atom 0) 0 user=> @my-atom 0
user=> (def my-atom (atom 0 :validator even?)) #'user/my-atom user=> @my-atom 0 user=> (swap! my-atom inc) IllegalStateException Invalid reference state clojure.lang.ARef.validate (ARef.java:33) user=> (swap! my-atom (partial + 2)) 2 user=> @my-atom 2
(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 ""}
