greyblake/aequitas

A Validations library. Someday.

This module provides validations for any Ruby class.

Specifying Validations¶ ↑

There are two primary ways to implement validations

1) Placing validation methods with properties as params in your class

require 'aequitas'

class ProgrammingLanguage
  include Aequitas

  attr_accessor :name

  validates_presence_of :name
end

2) (TODO) Using inferred validations on Virtus attributes, please see Aequitas::Inferred. Note that not all validations that are provided via validation methods, are also available as autovalidation options. If they are available, they’re functionally equivalent though.

class ProgrammingLanguage
  include Virtus
  include Aequitas

  attribute :name, String, :required => true
end

See Aequitas::Macros to learn about the complete collection of validation rules available.

Validating¶ ↑

Aequitas validations may be manually evaluated against a resource using the ‘#valid?` method, which will return true if the resource is valid, and false if it is invalid.

Working with Validation Errors¶ ↑

If an instance fails one or more validation rules, Aequitas::Violation instances will populate the Aequitas::ViolationSet object that is available through the #errors method.

For example:

my_account = Account.new(:name => "Jose")
if my_account.valid?
  # my_account is valid and has been saved
else
  my_account.errors.each do |e|
    puts e
  end
end

See Aequitas::ViolationSet for all you can do with the #errors method.

Contextual Validation¶ ↑

Aequitas also provide a means of grouping your validations into contexts. This enables you to run different sets of validations when you need it. For example, an instance may require separate validation rules depending on its state: publishing, exporting, importing and so on.

Again, using our example for pure Ruby class validations:

class ProgrammingLanguage
  include Virtus
  include Aequitas

  attribute :name, String

  def ensure_allows_manual_memory_management
    # ...
  end

  def ensure_allows_optional_parentheses
    # ...
  end

  validates_presence_of :name
  validates_with_method :ensure_allows_optional_parentheses,     :when => [:implementing_a_dsl]
  validates_with_method :ensure_allows_manual_memory_management, :when => [:doing_system_programming]
end

ProgrammingLanguage instance now use #valid? method with one of two context symbols:

@ruby.valid?(:implementing_a_dsl)       # => true
@ruby.valid?(:doing_system_programming) # => false

@c.valid?(:implementing_a_dsl)       # => false
@c.valid?(:doing_system_programming) # => true

Each context causes different set of validations to be triggered. If you don’t specify a context using :when, :on or :group options (they are all aliases and do the same thing), default context name is :default. When you do model.valid? (without specifying context explicitly), again, :default context is used. One validation can be used in two, three or five contexts if you like:

class Book
  include Virtus
  include Aequitas

  attribute :id,           Serial
  attribute :name,         String

  attribute :agreed_title, String
  attribute :finished_toc, Boolean

  # used in all contexts, including default
  validates_presence_of :name,         :when => [:default, :sending_to_print]
  validates_presence_of :agreed_title, :when => [:sending_to_print]

  validates_with_block :toc, :when => [:sending_to_print] do
    if self.finished_toc
      [true]
    else
      [false, "TOC must be finalized before you send a book to print"]
    end
  end
end

In the example above, name is validated for presence in both :default context and :sending_to_print context, while TOC related block validation and title presence validation only take place in :sending_to_print context.