ActiveRecord Validation: association saved even if validation failed

Errors are added to error object of record but associations are still saved.

  class Parent < ActiveRecord::Base
      validate :valid_child?

      #validation methods
      protected
      def valid_child?
         @child_names = Hash.new
         self.children.each do |curr_child|
            if @child_names[curr_child.name].nil?
                @child_names[curr_child.name] = curr开发者_如何学JAVA_child.name
            else
                errors.add(:base, "child name should be unique for children associated to the parent")
            end
         end
      end
      #associations
      has_and_belongs_to_many :children, :join_table => 'map__parents__children'
 end


#query on rails console

 @parent = Parent.find(1)
 @parent.children_ids = [1, 2]
 @parent.save

The problem is that, for an existing record, @parent.children_ids = [1, 2] will take effect a change in the database before the call to @parent.save.

Try using validates_associated to validate the children rather than rolling your own validation.

To make sure that the children's names are unique within the context of the parent, use validates_uniqueness_of with the :scope option to scope the uniqueness to the parent id. Something like:

class Child < ActiveRecord::Base
  belongs_to :parent
  validates_uniqueness_of :name, :scope => :parent
end