A simple ruby object validator
Ruby Gherkin
Latest commit 4c781b0 Jun 27, 2016 @zombor committed on GitHub Merge pull request #37 from solymosi/misc-improvements
Allow passing in class objects for rules + Upgrade to RSpec 3.4 + Misc improvements
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features Move everything under a Validator namespace Jun 16, 2012
lib Update readme and bump version Jun 27, 2016
.gitignore delete outdated documentation and it to the gitignore file Jul 29, 2015
Gemfile Upgrade to RSpec 3.4 and its expectation based syntax Jun 24, 2016
README.md Update readme and bump version Jun 27, 2016



Build Status

Validator is a simple ruby validation class. You don't use it directly inside your classes like just about every other ruby validation class out there. I chose to implement it in this way so I didn't automatically pollute the namespace of the objects I wanted to validate.

This also solves the problem of validating forms very nicely. Frequently you will have a form that represents many different data objects in your system, and you can pre-validate everything before doing any saving.


Validator is useful for validating the state of any existing ruby object.

  object = OpenStruct.new(:email => 'foo@bar.com', :password => 'foobar')
  validator = Validation::Validator.new(object)
  validator.rule(:email, [:email, :not_empty])             # multiple rules in one line
  validator.rule(:password, :not_empty)                    # a single rule on a line
  validator.rule(:password, :length => { :minimum => 3 })  # a rule that takes parameters

  if validator.valid?
    # save the data somewhere
    @errors = validator.errors

The first paramater can be any message that the object responds to.

Writing your own rules

If you have a custom rule you need to write, you can create a custom rule class for it:

  class MyCustomRule
    def error_key

    def valid_value?(value)
      # Logic for determining the validity of the value

    def params

A rule class should have the following methods on it:

  • error_key a symbol to represent the error. This shows up in the errors hash. Must be an underscored_version of the class name
  • valid_value?(value) the beef of the rule. This is where you determine if the value is valid or not
  • params the params hash that was passed into the constructor

If you add your custom rule class to the Validation::Rule namespace, you can reference it using a symbol:

  validator.rule(:field, :my_custom_rule)  # resolves to Validation::Rule::MyCustomRule
  validator.rule(:field, :my_custom_rule => { :param => :value })

Otherwise, just pass in the rule class itself:

  validator.rule(:field, MyProject::CustomRule)
  validator.rule(:field, MyProject::CustomRule => { :param => :value })

Writing self-contained validators

You can also create self-contained validation classes if you don't like the dynamic creation approach:

  require 'validation'
  require 'validation/rule/not_empty'

  class MyFormValidator < Validation::Validator
    include Validation

    rule :email, :not_empty

Now you can use this anywhere in your code:

  form_validator = MyFormValidator.new(OpenStruct.new(params))

Semantic Versioning

This project conforms to semver.


Have an improvement? Have an awesome rule you want included? Simple!

  1. Fork the repository
  2. Create a branch off of the master branch
  3. Write specs for the change
  4. Add your change
  5. Submit a pull request to merge against the master branch

Don't change any version files or gemspec files in your change.