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1.3.0 permalink

1.2.0
1.3.0

set-validator!

Sets the validator-fn for a var/ref/agent/atom. validator-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
validator-fn should return false or throw an exception. If the current state (root
value if var) is not acceptable to the new validator, an exception
will be thrown and the validator will not be changed.

1 Example top

link | changes
```
user=> (def atm (atom [2])
#'user/atm

user=> (set-validator! atm #(every? even? %))
nil

user=> (swap! atm into [5])
#<CompilerException java.lang.IllegalStateException: Invalid reference state (NO_SOURCE_FILE:0)>

user=> (set-validator! atm nil)
nil

user=> (swap! atm into [5]))
[2 5]
```
user=> (def atm (atom [2]) #'user/atm user=> (set-validator! atm #(every? even? %)) nil user=> (swap! atm into [5]) #<CompilerException java.lang.IllegalStateException: Invalid reference state (NO_SOURCE_FILE:0)> user=> (set-validator! atm nil) nil user=> (swap! atm into [5])) [2 5]

Source clojure/core.clj:2126 top

(defn set-validator!
  "Sets the validator-fn for a var/ref/agent/atom. validator-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
  validator-fn should return false or throw an exception. If the current state (root
  value if var) is not acceptable to the new validator, an exception
  will be thrown and the validator will not be changed."
  {:added "1.0"
   :static true}
  [^clojure.lang.IRef iref validator-fn] (. iref (setValidator validator-fn)))

Vars in clojure.core/set-validator!:

Used in 0 other vars

Comments top

1 comment(s) for set-validator!.

TimMc

link

If you want your validator to throw an exception with a useful message, make sure it is a RuntimeException (or subclass), otherwise ARef#validate will throw an IllegalStateException with a generic message.

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