Valcro

Valcro is the simple validation library for Ruby. It provides

• A declarative way to describe what makes an object valid
• A way to declare validator classes encapsulating validations to be shared across objects
• A method for running validations against an instance of your class
• A method for checking whether an object is valid
• Visibility into what validations failed

It is similar in spirit to ActiveModel's or Sequel's validations, but far simpler and with a slightly different API. It does not provide validation helpers such as validates_presence_of or similar.

require 'valcro'

class Dog
  include Valcro

  attr_accessor :name

  validate do
    errors.add(:name, 'must be great') unless name =~ /super|great|cool/
  end
end

dog = Dog.new
dog.name = 'spike'
dog.validate
dog.valid?
 => false
dog.errors[:name]
 => ["must be great"]
dog.error_messages
 => "name must be great"

Unlike other ruby validation libraries, you must call validate explicitely to check for validity of objects.

You may also have Cats in your system, which share the same validation. Valcro lets you encapsulate validations in an object with the following contract:

• It is constructed with the object being validated
• It responds to call, which receives a Valcro::ErrorList. Add validation errors to this object.

class GreatNameValidator
  def initialize(thing_with_name)
    @thing_with_name = thing_with_name
  end

  def call(errors)
    errors.add(:name, 'must be great') unless @thing_with_name.name =~ /super|great|cool/
  end
end

class Dog
  include Valcro
  attr_accessor :name
  validates_with GreatNameValidator
end

class Cat
  include Valcro
  attr_accessor :name
  validates_with GreatNameValidator
end

Valcro is copyright (c) Harold Giménez and is released under the terms of the MIT License found in the LICENSE file.