Rails:更新后无法保存对象!

我是rails开发的新手。 我在Post类中放置了一个自定义方法,在该方法中,我希望更新该Post类的特定属性/变量。我的方法如下:-

def update_bid_winner (winner_id)
  @bid_winner_id = winner_id
  puts @bid_winner_id
  save
  puts "post saved"
end

但是当我显示Post对象时,bid_winner_id变量仍然没有更新。
我怀疑在更新之后对象的保存不成功,因为
上面方法的puts-placed输出了我试图更新的正确值。

“我的rails服务器”窗口中的日志:-

2      <<< Output of the puts placed for debugging
post saved


Started GET "/posts/1/bids/1/offer_bid" for 127.0.0.1 at Sun Nov 21 13:21:59 +0530 2010
Processing by BidsController#offer_bid as HTML
Parameters: {"post_id"=>"1", "id"=>"1"}
User Load (3.1ms)  SELECT "users".* FROM "users" WHERE ("users"."id" = 1) LIMIT 1
Post Load (3.1ms)  SELECT "posts".* FROM "posts" WHERE ("posts"."id" = 1) LIMIT 1
Bid Load (0.5ms)  SELECT "bids".* FROM "bids" WHERE ("bids"."id" = 1) LIMIT 1
Redirected to http://localhost:3000/posts/1
Completed 302 Found in 167ms

我的帖子架构如下:-

create_table "posts", :force => true do |t|
t.integer  "user_id"
t.string   "title"
t.text     "body"
t.integer  "bid_winner_id"
end  

我在这里做错什么了???