Rails: How to limit number of items in has_many association (from Parent)

Question

I would like to limit the number of items in an association. I want to ensure the User doesn\'t have more than X Things. This question was asked before and the solution had th

Answer 1

You could try validates_length_of and validates_associated:

class Client < ActiveRecord::Base

  has_many :orders
  validates :orders, :length => { :maximum => 3 }

end

class Order < ActiveRecord::Base

  belongs_to :client
  validates_associated :client

end

A quick test shows that the valid? method works as expected, but it does not stop you from adding new objects.