ruby on rails - validates associated with model's error message

Question

I have two model as follows

class User < ActiveRecord::Base
 validates_associated :account
end

class Account < ActiveRecord::Base

  belongs_to :user

  #----------------------------------Validations--Start-------------------------
  validates_length_of :unique_url, :within => 2..30 ,:message => "Should be atleast 3 characters long!"
  validates_uniqueness_of :unique_url ,:message => "Already Taken"
  validates_format_of :unique_url,:with => /^([a-zA-Z0-9][a-zA-Z0-9-]*[a-zA-Z0-9])$/ , :message => " Cannot contain special charaters"
  #----------------------------------Validations--End---------------------------
end

Now when I associate an account to a user it says

"Account is invalid"

Instead I want to get the error message directly from that model. so it should say

"Should be atleast 3 characters long!" or "Already Taken" or " Cannot contain special charaters"

is there a way to do this ?

I don't want to give a generic message like :

validates_associated :account , :message=>"one of the three validations failed"

Answer 1

You can write your own custom validator, based on the code for the built-in validator.

Looking up the source code for validates_associated, we see that it uses the "AssociatedValidator". The source code for that is:

module ActiveRecord
  module Validations
    class AssociatedValidator < ActiveModel::EachValidator
      def validate_each(record, attribute, value)
        if Array.wrap(value).reject {|r| r.marked_for_destruction? || r.valid?}.any?
          record.errors.add(attribute, :invalid, options.merge(:value => value))
        end
      end
    end

    module ClassMethods
      
      def validates_associated(*attr_names)
        validates_with AssociatedValidator, _merge_attributes(attr_names)
      end
    end
  end
end

So you can use this as an example to create a custom validator that bubbles error messages like this (for instance, add this code to an initializer in config/initializers/associated_bubbling_validator.rb):

module ActiveRecord
  module Validations
    class AssociatedBubblingValidator < ActiveModel::EachValidator
      def validate_each(record, attribute, value)
        ((value.kind_of?(Enumerable) || value.kind_of?(ActiveRecord::Relation)) ? value : [value]).each do |v|
          unless v.valid?
            v.errors.full_messages.each do |msg|
              record.errors.add(attribute, msg, options.merge(:value => value))
            end
          end
        end
      end
    end

    module ClassMethods
      def validates_associated_bubbling(*attr_names)
        validates_with AssociatedBubblingValidator, _merge_attributes(attr_names)
      end
    end
  end
end

So you can now validate like so:

class User < ActiveRecord::Base
 validates_associated_bubbling :account
end

Also, be sure to add a validate: false in your has_many association, otherwise, Rails will validate the association by default and you'll end up with two error messages, one given by your new AssociatedBubblingValidator and one generic given by Rails.