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好吧,我的第一个项目的主要问题是速度。我不知道在内存和数据库调用之间哪个是哪个。我有两个问题:内存和数据库调用之间的区别
- 如何区分数据库调用和内存调用(如果这是它的调用方式)?
我曾遇到一个指向
`r.status_messages.last.name`
所以我测试了它在轨控制台(我这是 我的第一个问题相关的感觉。)
总之一个未定义的方法错误,- r.status_messages.last.name不起作用(读作2级的命令,r.status_messages.last &。名称)
- BUT, h = r.status_messages.last然后h.name,WORKS
- 但是,当我这样做,r.status_messages.last.name,它现在工作。
这里发生了什么?
细节
request_form的has_many status_messages:通过request_statuses
的Rails 3.2.3,Ruby193,Windows 7的教授,NetBeans IDE的6.9.1
Rails的控制台
r = RequestForm.find(25)
r = RequestForm.find(25)
[1m[35mRequestForm Load (1.0ms)[0m SELECT `request_forms`.* FROM `request_forms` WHERE `request_forms`.`id` = ? LIMIT 1 [["id", 25]]
#<RequestForm id: 25, control_no: 1, requested: true, cds_requested: nil, cds_returned: nil, approval: false, cds_released: nil, cds_recycled: nil, defective_cds: 0, request_date: "2012-05-30", released_date: nil, user_id: 3, admin_id: nil, remarks: nil, created_at: "2012-05-30 07:13:50", updated_at: "2012-05-30 07:13:50">
r.status_messages
r.status_messages
[#<StatusMessage id: 1, description: "can be edited until sent", user_id: nil, created_at: "2012-05-30 07:31:02", updated_at: "2012-05-30 07:31:02", name: "Created">, #<StatusMessage id: 2, description: "visible to admin", user_id: nil, created_at: "2012-05-30 07:32:51", updated_at: "2012-05-30 07:32:51", name: "Sent">]
[1m[36mStatusMessage Load (1.0ms)[0m [1mSELECT `status_messages`.* FROM `status_messages` INNER JOIN `request_statuses` ON `status_messages`.`id` = `request_statuses`.`status_message_id` WHERE `request_statuses`.`request_form_id` = 25[0m
r.status_messages.last
r.status_messages.last
#<StatusMessage id: 2, description: "visible to admin", user_id: nil, created_at: "2012-05-30 07:32:51", updated_at: "2012-05-30 07:32:51", name: "Sent">
r.status_messages.last
.name
r.status_messages.last
#<StatusMessage id: 2, description: "visible to admin", user_id: nil, created_at: "2012-05-30 07:32:51", updated_at: "2012-05-30 07:32:51", name: "Sent">
.name
SyntaxError: (irb):6: syntax error, unexpected '.'
.name
^
from C:/Ruby193/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/commands/console.rb:47:in `start'
from C:/Ruby193/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/commands/console.rb:8:in `start'
from C:/Ruby193/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/commands.rb:41:in `<top (required)>'
from script/rails:6:in `require'
from script/rails:6:in `<main>'
r.status_messages.last
.description
r.status_messages.last
#<StatusMessage id: 2, description: "visible to admin", user_id: nil, created_at: "2012-05-30 07:32:51", updated_at: "2012-05-30 07:32:51", name: "Sent">
.description
SyntaxError: (irb):10: syntax error, unexpected '.'
.description
^
from C:/Ruby193/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/commands/console.rb:47:in `start'
from C:/Ruby193/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/commands/console.rb:8:in `start'
from C:/Ruby193/lib/ruby/gems/1.9.1/gems/railties-3.2.3/lib/rails/commands.rb:41:in `<top (required)>'
from script/rails:6:in `require'
from script/rails:6:in `<main>'
h = r.status_messages.last
h = r.status_messages.last
#<StatusMessage id: 2, description: "visible to admin", user_id: nil, created_at: "2012-05-30 07:32:51", updated_at: "2012-05-30 07:32:51", name: "Sent">
h.name
h.name
"Sent"
r.status_messages.last.name
r.status_messages.last.name
"Sent"
r.status_messages.last.description
r.status_messages.last.description
"visible to admin"
编辑:我已经说过这个问题,关于划分到两个查询。对不起,不清楚。
我输入r.status_messages.last.name
然后按下进入
但轨道控制台已经削减到r.status_messages.last
和.name
。这导致了语法错误。
name
和description
是状态消息的属性。
然而,当我救r.status_messages.last
一个变量h
h.name
和h.description
工作。
令人惊讶的是:之后r.status_messages.last.name
也运行良好。
- 如何区分数据库调用和内存调用(如果这是它的调用方式)? 我想要一个很好的参考,其中有一个表或比较列表,如
.size
是.length
。 - 是什么导致了这个部门?
请亲自看看你的代码。我敢打赌,你也会看到语法错误消息。 – rubish
我不清楚控制台的所有输出是什么,但是在错误情况下,如“.description”,看起来“.description”是在它自己的行上,这实际上是一个语法错误,如上所示。 –
感谢@rubish,在rails控制台将它切成两半之后,语法当然是错误的。任何想法是什么造成的? –