如何在rails中创建postgres触发器？

Question

我有一个表产品(id,name)和表product_raiting(product_id,rate_type,rate).当我创建新产品时,我需要为此产品创建三个raitings.

如何添加postgres触发器,例如:

    product.create
    product.product_raitings.create( :rate_type => 0, :rate => 0 )
    product.product_raitings.create( :rate_type => 1, :rate => 0 )
    product.product_raitings.create( :rate_type => 2, :rate => 0 )
    product.product_raitings.create( :rate_type => 3, :rate => 0 )

请帮忙.

Answer 1

你想在数据库中创建一个触发器,这样插入数据库就可以了吗？

http://www.postgresql.org/docs/9.1/static/sql-createtrigger.html

CREATE FUNCTION addRaitings() RETURNS TRIGGER AS '
   BEGIN
      INSERT INTO product_raitings(product_id,rate_type,rate) values(NEW.id,0,0);
      INSERT INTO product_raitings(product_id,rate_type,rate) values(NEW.id,1,0);
      INSERT INTO product_raitings(product_id,rate_type,rate) values(NEW.id,2,0);
      INSERT INTO product_raitings(product_id,rate_type,rate) values(NEW.id,3,0);
   END;
   ' LANGUAGE plpgsql;

CREATE TRIGGER createRaitingTrigger
        AFTER INSERT ON products
        FOR EACH ROW
        EXECUTE PROCEDURE addRaitings();

或者你想让rails做这项工作？然后它将是一个after_create回调 http://api.rubyonrails.org/classes/ActiveRecord/Callbacks.html

所以也许是这样的.

class Product < ActiveRecord::Base
  has_many product_raitings

  after_create :build_default_raitings

 private
 def build_default_raitings
    (0..3).each { |x| self.product_raitings.create(:rate_type => x, :rate => 0) }
 end
end