instance method validates_acceptance_of

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 are :create and :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 (for example, :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.