Rails - Validate Presence Of Association?

ruby-on-rails ruby-on-rails-3 validation activerecord
skaz picture skaz · Apr 16, 2011 · Viewed 63.5k times · Source

I have a model A that has a "has_many" association to another model B. I have a business requirement that an insert into A requires at least 1 associated record to B. Is there a method I can call to make sure this is true, or do I need to write a custom validation?

Answer

fl00r picture fl00r · Apr 17, 2011

You can use validates_presence_of http://apidock.com/rails/ActiveModel/Validations/ClassMethods/validates_presence_of

class A < ActiveRecord::Base
  has_many :bs
  validates_presence_of :bs
end

or just validates http://apidock.com/rails/ActiveModel/Validations/ClassMethods/validates

class A < ActiveRecord::Base
  has_many :bs
  validates :bs, :presence => true
end

But there is a bug with it if you will use accepts_nested_attributes_for with :allow_destroy => true: Nested models and parent validation. In this topic you can find solution.

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