Ruby Datamapper计数不起作用 [英] Ruby Datamapper count not working

问题描述

在执行操作时来自irb:

From irb when I do:

Router.all(:email=>"[e-mail]")

我获得了与该电子邮件关联的所有路由器的列表.但是当我这样做时:

I get a list of all the routers associated with that email. But when I do:

Router.count(:email=>"[e-mail]")

我总是得到0

我也研究了这个问题: Ruby Datamapper .count始终返回0 ，但我仍然不知道为什么它不起作用.

I've also looked at this question: Ruby Datamapper .count always returns 0 but I still don't know why it isn't working.

-更新#1-

这是Router.all命令的输出.如您所见，我得到了结果.

Here is the output of the Router.all command. As you can see I get results back.

1.9.3-p362 :003 > Router.all(:email=>"[e-mail]")
=> [#<Router @id=8 @email="[e-mail]" @hostname="router0">, #<Router @id=9              @email="[e-mail]" @hostname="router0">, #<Router @id=10 @email="[e-mail]" @hostname="router0">, #<Router @id=11 @email="[e-mail]" @hostname="router0">, #<Router @id=13 @email="[e-mail]" @hostname="router0">, #<Router @id=14 @email="[e-mail]" @hostname="router0">, #<Router @id=15 @email="[e-mail]" @hostname="router0">, #<Router @id=16 @email="[e-mail]" @hostname="router0">] 

但是当我按照建议执行Router.count时，它仍然返回0

But when I do Router.count as suggested it still is returning 0

1.9.3-p362 :004 > Router.count(:conditions => ["email = ?", "[e-mail]"])
=> 0 

1.9.3-p362 :005 > Router.count(:conditions => "email = '[e-mail]'")
=> 0 

推荐答案

您可以require 'dm-aggregates'，之后您可以

Router.count(:email => "[e-mail]")

它将转化为

SELECT COUNT(*) FROM routers WHERE "email" = '[e-mail]'

(尽管您会在Router.all(:email => "[e-mail]").count和dm-aggregates中得到相同的语句.)

(Although you'll get the same statement with Router.all(:email => "[e-mail]").count with dm-aggregates.)

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