Rails的ActiveRecord的屬性=

Question

我這樣做：

@person.attributes = params[:person] 

誰能給我一個線索，爲什麼做的屬性=會引起一串SQL中我的日誌顯示？

我看到幾個SELECT甚至更新。

我發誓我沒做一個「保存」 - 所以我不知道爲什麼設置屬性會觸發查詢。

我是否缺少after_ filter？

謝謝。

Answer 1

就我所知，在標準模型上設置屬性不會導致任何SELECT或UPDATE調用。這還可以看出，當我運行一個腳本/控制檯會話併發登錄是真實的：

>> f = Forum.first 

==> ./log/development.log <== 
    SQL (0.1ms) SET SQL_AUTO_IS_NULL=0 
    Forum Load (0.4ms) SELECT * FROM `forums` ORDER BY title asc LIMIT 1 
    Forum Columns (12.6ms) SHOW FIELDS FROM `forums` 
=> #<Forum id: 1, title: "Welcome to rBoard!", description: "This is an example forum for Rboard.", is_visible_to_id: nil, topics_created_by_id: nil, position: 1, parent_id: nil, last_post_id: 1, last_post_forum_id: nil, topics_count: 1, posts_count: 4, category_id: nil, active: true, open: true> 
>> f.attributes 
=> {"position"=>1, "is_visible_to_id"=>nil, "open"=>true, "topics_count"=>1, "title"=>"Welcome to rBoard!", "last_post_forum_id"=>nil, "posts_count"=>4, "id"=>1, "category_id"=>nil, "parent_id"=>nil, "topics_created_by_id"=>nil, "last_post_id"=>1, "description"=>"This is an example forum for Rboard.", "active"=>true} 
>> f.attributes = _ 
=> {"position"=>1, "is_visible_to_id"=>nil, "open"=>true, "topics_count"=>1, "title"=>"Welcome to rBoard!", "last_post_forum_id"=>nil, "posts_count"=>4, "id"=>1, "category_id"=>nil, "parent_id"=>nil, "topics_created_by_id"=>nil, "last_post_id"=>1, "description"=>"This is an example forum for Rboard.", "active"=>true} 

你可以在這裏看到，有隻有兩個得到執行SQL查詢，一來獲取Forum記錄和另一個查找forums表中的列。

它不是直到我保存它，它做了一些疑問：

>> f.attributes 
=> {"position"=>1, "is_visible_to_id"=>nil, "open"=>true, "topics_count"=>1, "title"=>"Welcome to rBoard!", "last_post_forum_id"=>nil, "posts_count"=>4, "id"=>1, "category_id"=>nil, "parent_id"=>nil, "topics_created_by_id"=>nil, "last_post_id"=>1, "description"=>"This is an example forum for Rboard.", "active"=>true} 
>> attr = _ 
=> {"position"=>1, "is_visible_to_id"=>nil, "open"=>true, "topics_count"=>1, "title"=>"Welcome to rBoard!", "last_post_forum_id"=>nil, "posts_count"=>4, "id"=>1, "category_id"=>nil, "parent_id"=>nil, "topics_created_by_id"=>nil, "last_post_id"=>1, "description"=>"This is an example forum for Rboard.", "active"=>true} 
>> attr["position"] = 2 
=> 2 
>> f.save 
    SQL (0.2ms) BEGIN 
=> true 
>> SQL (0.2ms) COMMIT 
f.attributes = attr 
=> {"position"=>2, "is_visible_to_id"=>nil, "open"=>true, "topics_count"=>1, "title"=>"Welcome to rBoard!", "last_post_forum_id"=>nil, "posts_count"=>4, "id"=>1, "category_id"=>nil, "parent_id"=>nil, "topics_created_by_id"=>nil, "last_post_id"=>1, "description"=>"This is an example forum for Rboard.", "active"=>true} 
>> WARNING: Can't mass-assign these protected attributes: id 
f.save 
    SQL (0.2ms) BEGIN 
    Forum Update (20.3ms) UPDATE `forums` SET `position` = 2 WHERE `id` = 1 
    SQL (27.2ms) COMMIT 
=> true