Encapsulates the pattern of wanting to validate the acceptance of a terms of service check box (or similar agreement). Example:

class Person < ActiveRecord::Base
  validates_acceptance_of :terms_of_service
  validates_acceptance_of :eula, :message => "must be abided"
end

If the database column does not exist, the terms_of_service attribute is entirely virtual. This check is performed only if terms_of_service is not nil and by default on save.

Configuration options:

• message - A custom error message (default is: "must be accepted")
• on - Specifies when this validation is active (default is :save, other options :create, :update)
• allow_nil - Skip validation if attribute is nil. (default is true)
• accept - Specifies value that is considered accepted. The default value is a string "1", which makes it easy to relate to an HTML checkbox. This should be set to ‘true’ if you are validating a database column, since the attribute is typecast from "1" to true before validation.
• if - Specifies a method, proc or string to call to determine if the validation should occur (e.g. :if => :allow_validation, or :if => Proc.new { |user| user.signup_step > 2 }). The method, proc or string should return or evaluate to a true or false value.
• unless - Specifies a method, proc or string to call to determine if the validation should not occur (e.g. :unless => :skip_validation, or :unless => Proc.new { |user| user.signup_step <= 2 }). The method, proc or string should return or evaluate to a true or false value.

Source Code

# File active_record/validations.rb, line 462
def validates_acceptance_of(*attr_names)
  configuration = { :message => ActiveRecord::Errors.default_error_messages[:accepted], :on => :save, :allow_nil => true, :accept => "1" }
  configuration.update(attr_names.extract_options!)

  db_cols = begin
    column_names
  rescue ActiveRecord::StatementInvalid
    []
  end
  names = attr_names.reject { |name| db_cols.include?(name.to_s) }
  attr_accessor(*names)

  validates_each(attr_names,configuration) do |record, attr_name, value|
    record.errors.add(attr_name, configuration[:message]) unless value == configuration[:accept]
  end
end