Rails: validate uniqueness of two columns (together)
You can use a uniqueness validation with the scope
option.
Also, you should add a unique index to the DB to prevent new records from passing the validations when checked at the same time before being written:
class AddUniqueIndexToReleases < ActiveRecord::Migration def change add_index :releases, [:country, :medium], unique: true endendclass Release < ActiveRecord::Base validates :country, uniqueness: { scope: :medium }end
All the above answers are missing how to validate the uniqueness of multiple attributes in a model. The code below intends to tell how to use multiple attributes in a scope.
validates :country, uniqueness: { scope: [:medium, :another_medium] }
It validates uniqueness of country
in all rows with values of medium
and another_medium
.
Note: Don't forget to add an index on the above column, this insures fast retrieval and adds a DB level validation for unique records.
Update: For adding an index while creating table
t.index [:medium, :another_medium], unique: true
You can pass a :scope
parameter to your validator like this:
validates_uniqueness_of :medium, scope: :country
See the documentation for some more examples.