I was wandering why in books like Agile Web Development with Rails there's no mention to validates_whatever_of way of validating, all validation examples are done using validates :attr, :whatever => true ? I've just started learning Rails and this made me confused!
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2 Answers
In Rails 2.x, where you would have said something like:
validates_presence_of :user_name
in 3.x, you now do:
validates :username, :presence => true
The old way is still supported, I think, but it is deprecated.
It's really just a different way of expressing the same thing. While older books and tutorials will use the former, it should be fairly simple to translate that to 3.x style. See http://api.rubyonrails.org/classes/ActiveModel/Validations/ClassMethods.html#method-i-validates for example.
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The validates syntax is just a new shortcut for the same thing. It's especially useful when you're validating a bunch of attributes with similar limits. So this:
validates_presence_of :one
validates_presence_of :two
validates_presence_of :three
validates_presence_of :four
can be reduced to
validates :one, :two, :three, :four, :presence => true
It's also a nice, consistent interface to custom validators.
3 Comments
Ansd
but
validates_presence_of :one, :two, :three, :four also works
Rob Davis
Ah, I guess that's true. :-) It's probably contrived, but in the new scheme you can also validate other aspects using
validates besides "presence" by tacking them onto validates. The best argument for the new scheme is that it's extensible without monkey patching ActiveRecord::Base. As in the example I liked to above, you can add a custom validator and it becomes available as option to validates. For example, creating an EmailValidator makes :valid => true available.Rob Davis
Err, I meant
:email => true, but you get the idea.