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Map validation library for Clojure
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Map validation library for Clojure and ClojureScript


Most other validation libraries (such as valip) assume validation is done per key, rather than on a map as a whole. This makes it difficult to write multi-key validations. Validation functions in Verily take an entire map, making multi-key (or single-key) validations easy.

Verily also provides a declarative, data-oriented API in addition to a conventional, function-oriented API. Using data to describe validations has benefits in certain use cases. For instance, you can share validation specifications between Clojure and ClojureScript.



[jkkramer/verily "0.6.0"]


(ns example.core
  (:require [jkkramer.verily :as v]))

There are two ways to validate a map:

  1. With a validation specification - i.e., data, which Verily turns into a validation function for you
  2. With a validation function

To validate using a validation specification:

(def validations
  [[:required [:foo :bar :password]]
   [:equal [:password :confirm-password] "Passwords don't match, dummy"]
   [:min-length 8 :password]])

(v/validate {:foo "foo"
             :password "foobarbaz"
             :password-confirm "foobarba"}
;; Returns:
({:keys (:bar), :msg "must not be blank"}
 {:keys [:password :confirm-password], :msg "Passwords don't match, dummy"})

To turn a validation specification into a function yourself:

(def validator (v/validations->fn validations))

You can use validation functions instead of data if you prefer. This makes it easier to write your own:

;; Custom validator
(defn validate-password [m]
  (when (#{"12345" "password" "hunter2"} (:password m))
    {:keys [:password] :msg "You can't use that password"}))

;; Combine several built-in validators and our own custom one
(def validator
    (v/required [:foo :bar :password])
    (v/equal [:password :password-confirm])
    (v/min-length 8 :password)

(validator {:foo "foo"
            :password "foobarbaz"
            :password-confirm "foobarba"})
;; Returns:
({:keys (:bar), :msg "must not be blank"}
 {:keys [:password :password-confirm], :msg "must be equal"})

Validation Function Contract

The contract for a validation function is:

  • Take a map as an argument
  • If validation succeeded, return nil or an empty collection. If there was a problem, return a problem map or collection of problem maps. Each problem is a map with the following keys:
    • :keys (optional) - relevant map keys
    • :msg - description of the problem

Built-in Validations

All validation specifications accept a key or sequence of keys. The message is always optional.

Keys can be dotted keywords such as, which will be interpreted as a nested path (if the key does not exist in the top-level map). Strings such as "foo[bar]" are also allowed, and have the same semantics.

Unless :required is used, all validations allow the keys to be absent from the map, or have a nil value (or blank if a string-based type).

  • :required <keys> [msg] - must not be absent, blank, or nil
  • :contains <keys> [msg] - must not be absent, but can be blank or nil
  • :not-blank <keys> [msg] - may be absent but not blank or nil
  • :exact <value> <keys> [msg] - must be a particular value
  • :equal <keys> [msg] - all keys must be equal
  • :email <keys> [msg] - must be a valid email
  • :url <keys> [msg] - must be a valid URL
  • :web-url <keys> [msg] - must be a valid website URL (http or https)
  • :link-url <keys> [msg] - must be a valid link URL (can be relative, http: or https: may be omitted)
  • :matches <regex> <keys> [msg] - must match a regular expression
  • :min-length <len> <keys> [msg] - must be a certain length (for strings or collections)
  • :max-length <len> <keys> [msg] - must not exceed a certain length (for strings or collections)
  • :complete <keys> [msg] - must be a collection with no blank or nil values
  • :min-val <min> <keys> [msg] - must be at least a certain value
  • :max-val <max> <keys> [msg] - must be at most a certain value
  • :within <min> <max> <keys> [msg] - must be within a certain range (inclusive)
  • :positive <keys> [msg] - must be a positive number
  • :negative <keys> [msg] - must be a negative number
  • :after <date> <keys> [msg] - must be after a certain date
  • :before <date> <keys> [msg] - must be before a certain date
  • :in <coll> <keys> [msg] - must be contained within a collection
  • :every-in <coll> <keys> [msg] - each value must be within a collection (for values that are themselves collections)
  • :us-zip <keys> [msg] - must be a valid US zip code
  • :luhn <keys> [msg] - must be pass the Luhn check (e.g., for credit card numbers)
  • Datatype validations: :string, :boolean, :integer, :float, :decimal, :date (plus aliases)
  • Datatype collection validations: :strings, :booleans, :integers, :floats, :decimals, :dates (plus aliases)

All validation specifications have corresponding validator functions in the jkkramer.verily namespace, if you prefer to use those directly.


Copyright © 2012-2013 Justin Kramer

Distributed under the Eclipse Public License, the same as Clojure.

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