Question

In my Rails App, I have a Like model.

### like.rb
### Custom Validator Code:
class UniquenessValidator < ActiveModel::Validator
  def validate(record)
      # Empty   
  end
end

class Like < ActiveRecord::Base
  include ActiveModel::Validations
  validates_with UniquenessValidator

  attr_accessible :user_id

  belongs_to :likeable, polymorphic: true
  belongs_to :user
end

In my rails console I try to do Like.all ( currently my Likes table is empty )

1.9.2p320 :001 > Like.all
RuntimeError: :attributes cannot be blank
        from /Users/user/.rvm/gems/ruby-1.9.2-p320@test_app/gems/activemodel-3.2.3/lib/active_model/validator.rb:141:in `initialize'
        from /Users/user/.rvm/gems/ruby-1.9.2-p320@test_app/gems/activerecord-3.2.3/lib/active_record/validations/uniqueness.rb:7:in `initialize'
        from /Users/user/.rvm/gems/ruby-1.9.2-p320@test_app/gems/activemodel-3.2.3/lib/active_model/validations/with.rb:84:in `new'
        from /Users/user/.rvm/gems/ruby-1.9.2-p320@test_app/gems/activemodel-3.2.3/lib/active_model/validations/with.rb:84:in `block in validates_with'
        from /Users/user/.rvm/gems/ruby-1.9.2-p320@test_app/gems/activemodel-3.2.3/lib/active_model/validations/with.rb:83:in `each'
        from /Users/user/.rvm/gems/ruby-1.9.2-p320@test_app/gems/activemodel-3.2.3/lib/active_model/validations/with.rb:83:in `validates_with'
        from /Users/user/Programming/WWW/Rails/experiments/test_app/app/models/like.rb:3:in `<class:Like>'
        from /Users/user/Programming/WWW/Rails/experiments/test_app/app/models/like.rb:1:in `<top (required)>'
        from /Users/user/.rvm/gems/ruby-1.9.2-p320@test_app/gems/activesupport-3.2.3/lib/active_support/dependencies.rb:469:in `load'
        from /Users/user/.rvm/gems/ruby-1.9.2-p320@test_app/gems/activesupport-3.2.3/lib/active_support/dependencies.rb:469:in `block in load_file'
        from /Users/user/.rvm/gems/ruby-1.9.2-p320@test_app/gems/activesupport-3.2.3/lib/active_support/dependencies.rb:639:in `new_constants_in'
        from /Users/user/.rvm/gems/ruby-1.9.2-p320@test_app/gems/activesupport-3.2.3/lib/active_support/dependencies.rb:468:in `load_file'
        from /Users/user/.rvm/gems/ruby-1.9.2-p320@test_app/gems/activesupport-3.2.3/lib/active_support/dependencies.rb:353:in `require_or_load'
        from /Users/user/.rvm/gems/ruby-1.9.2-p320@test_app/gems/activesupport-3.2.3/lib/active_support/dependencies.rb:502:in `load_missing_constant'
        from /Users/user/.rvm/gems/ruby-1.9.2-p320@test_app/gems/activesupport-3.2.3/lib/active_support/dependencies.rb:192:in `block in const_missing'
        from /Users/user/.rvm/gems/ruby-1.9.2-p320@test_app/gems/activesupport-3.2.3/lib/active_support/dependencies.rb:190:in `each'
        from /Users/user/.rvm/gems/ruby-1.9.2-p320@test_app/gems/activesupport-3.2.3/lib/active_support/dependencies.rb:190:in `const_missing'
        from (irb):1
        from /Users/user/.rvm/gems/ruby-1.9.2-p320@test_app/gems/railties-3.2.3/lib/rails/commands/console.rb:47:in `start'
        from /Users/user/.rvm/gems/ruby-1.9.2-p320@test_app/gems/railties-3.2.3/lib/rails/commands/console.rb:8:in `start'
        from /Users/user/.rvm/gems/ruby-1.9.2-p320@test_app/gems/railties-3.2.3/lib/rails/commands.rb:41:in `<top (required)>'
        from script/rails:6:in `require'
        from script/rails:6:in `<main>'
1.9.2p320 :002 > 

What is going on here ? (btw if I remove the validates_with UniquenessValidator from Like.rb , I don’t get this error)

Answer 1

Call your validator MyUniquenessValidator.

UniquenessValidator already exists in activerecord. This string from /Users/user/.rvm/gems/ruby-1.9.2-p320@test_app/gems/activerecord-3.2.3/lib/active_record/validations/uniqueness.rb:7:ininitialize’` is telling you about it.

Be careful with predefined ruby and RoR classes (data types (for example, “Complex”), rails validators, etc.)