why does rails not accept the :message symbol outside of a nested hash option?

Question

Here is my code. The first commented line works fine; the second doesn't. The documentation is sketchy here - no mention of the :message option under the "validates" method, but "validates_format_of" says :message is fine. (http://apidock.com/rails/ActiveModel/Validations/ClassMethods/validates) What is going on here?

class Product < ActiveRecord::Base
  validates :title, :description, :image_url, :presence => true
  #validates :title, :length => {:minimum => 10, :message => "help!"}
  #validates :title, :length => {:minimum => 10}, :message => "help!"
  validates :price, :numericality => {:greater_than_or_equal_to => 0.01}
  validates :image_url, :format => {
    :with => %r{\.(gif|jpg|png)$}i,
    :message => 'must be a URL for GIF, JPG or PNG image.'
  }
end

Answer 1

In the first commented line, the message value is an option to the :length parameter and it appears its being ignored. To test try

validates :title, :length => {:minimum => 10, :foobar => "help!"}

and you will find it to works without creating an error.

validates is just a shortcut to default validators. You seem to want to set the validates_format_of :message options, so I think you want something like:

validates :title, length => {:minimum => 10}, :format => { :message => "help!" }

Answer 2

Length validations are baked in:

validates_length_of :title, :minimum => 10, :message => "help!"

Active Record Validations