by Akiva Leeder & Rex Feng @ Flatiron School 2012
Extend ActiveRecord validations by checking if entries in a form are identical. Normal rails uniqueness validations work by checking for duplicate entries in the database, but that does not work when checking for unique form values before they are submitted to the database.
For example, in a Question model that has_many Choices, this gem will throw an error that prohibits the data from saving if the choices that pertain to that question instance are identical. If the Question "What color is the sky?" has Choices "Blue", "Blue", and "Green", this gem provides validation that the question cannot be saved due to the duplication of the "Blue" choice.
Include gem in your Gemfile
gem "validate_uniqueness_of_in_memory
In the command line, run bundle. You should see "Installing validate_uniqueness_of_in_memory (0.0.X)", where X is the current gem version.
$ bundle
In the parent model (the model that has_many relationship), add the following code:
validate :validate_unique_CHILD-MODEL-NAME
def validate_unique_CHILD-MODEL-NAME
validate_uniqueness_of_in_memory(:CHILD-MODEL-NAME, [CHILD-ATTRIBUTE-TO-VALIDATE-UNIQUENESS, PARENT-ID], 'ERROR MESSAGE GOES HERE.')
end
An example of parent model code:
class Question < ActiveRecord::Base
attr_accessible :name, :choices, :choices_attributes
has_many :choices
accepts_nested_attributes_for :choices
validate :validate_unique_choices
def validate_unique_choices
validate_uniqueness_of_in_memory(:choices, [:name, :question_id], 'Choices must be unique.')
end
end
An example of child model code:
class Choice < ActiveRecord::Base
attr_accessible :name, :question_id
belongs_to :question
end