/ Ruby on Rails
/
method

validate

validate(*methods, &block)
public

Adds a validation method or block to the class. This is useful when overriding the #validate instance method becomes too unwieldly and you’re looking for more descriptive declaration of your validations.

This can be done with a symbol pointing to a method: 

  class Comment < ActiveRecord::Base
    validate :must_be_friends

    def must_be_friends
      errors.add_to_base("Must be friends to leave a comment") unless commenter.friend_of?(commentee)
    end
  end

Or with a block which is passed the current record to be validated: 

  class Comment < ActiveRecord::Base
    validate do |comment|
      comment.must_be_friends
    end

    def must_be_friends
      errors.add_to_base("Must be friends to leave a comment") unless commenter.friend_of?(commentee)
    end
  end

This usage applies to #validate_on_create and #validate_on_update as well.

4Notes

Is it really deprecated?

rob-twf · Jul 21, 200810 thanks

I think the deprecation notice is in the wrong place, it is actually the instance method ActiveRecord::Validations#validate that has been deprecated.

The same applies to ActiveRecord::Validations#validate_on_create and ActiveRecord::Validations#validate_on_update: they have both been deprecated in favour of the class methods validate_on_create and validate_on_update.

More on deprecation

rxcfc · Oct 7, 20084 thanks

This is not deprecated. I think the docs are confused because the validate, validate_on_create, and validate_on_update methods are actually callbacks and not explicitly defined on their own. The correct usage is the same as in the docs above.

You can call several times

szeryf · May 31, 20092 thanks

You can call it several times, like:

class Comment < ActiveRecord::Base
validate :must_be_friends
validate :must_be_awesome
...

or with several arguments:

class Comment < ActiveRecord::Base
validate :must_be_friends, :must_be_awesome
...

You can call it with an { :on => ~~~ } as the last argument

larry333 · Feb 17, 20112 thanks

For example: validate :must_be_friends, :on => :create