DynamicUniquenessValidator

Adds the ability to validate two fields at the same time. For an intermediate table with many-to-many association

Add to your Gemfile:

gem 'dynamic_uniqueness_validator'

And then execute:

$ bundle install

Add inverse_of to model with has_many. Then add the following to your model:

$ validates :my_model_item, dynamic_uniqueness: { parent_association: :parent_model, child_association: :model_item }

You can also use the message option

$ validates :my_model_item, dynamic_uniqueness: { parent_association: :parent_model, child_association: :model_item, message: "Custom error message" }

The gem is available as open source under the terms of the MIT License.