method

validate

Importance_5
v2.0.3 - Show latest stable - 4 notes - Class: ActiveRecord::Validations::ClassMethods
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.

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July 21, 2008 - (v2.0.3 - v2.1.0)
10 thanks

Is it really deprecated?

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.

October 7, 2008 - (v2.0.3 - v2.1.0)
4 thanks

More on deprecation

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.

May 31, 2009
2 thanks

You can call several times

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
  ...
February 17, 2011
2 thanks

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

For example:

validate :must_be_friends, :on => :create