Rails 3：如何使用相关对象上的方法？
我正在使用 Rails 3.1 更新网站并添加一些功能。该应用程序跟踪一组站点的测试。最初，我将每个测试的成绩存储为“测试”表中的一列，但现在我创建了一个名为“评论”的新模型，以保存每个测试分配的成绩和评论的历史记录。模型如下所示：
class Site < ActiveRecord::Base
has_many :tests
has_many :reviews, :through => :tests
class Test < ActiveRecord::Base
has_many :reviews
belongs_to :site
class Review < ActiveRecord::Base
belongs_to :test
has_one :user
以前，我可以在站点模型中执行类似的操作来获取有关成绩的一些报告数据：
def total_a_grades
tests.count(:conditions => "reviewer_grade = 4 and review_status = 3")
end
由于成绩现在不在测试模型中，我创建了此方法来访问每个测试的最新成绩
def last_grade
return reviews.find(:last).grade
end
：可以很好地在测试视图中显示最新的成绩，但如何在站点级别使用它？由于该值现在采用的方法未存储在数据库中，因此我不知道如何使用它，并且在主要的在线教程/截屏网站上找不到与此相关的任何内容。
预先感谢您的帮助！
I'm updating a site with Rails 3.1 and adding some features. This application tracks tests for a collection of sites. Originally I was storing the grade for each test as a column in the Tests table but now I have created a new model called Reviews to keep a history of grades and comments assigned each test. The models look like this:
class Site < ActiveRecord::Base
has_many :tests
has_many :reviews, :through => :tests
class Test < ActiveRecord::Base
has_many :reviews
belongs_to :site
class Review < ActiveRecord::Base
belongs_to :test
has_one :user
Previously I could do something like this in the Site model to get some reporting data on grades:
def total_a_grades
tests.count(:conditions => "reviewer_grade = 4 and review_status = 3")
end
Since the grades are now out of the Test model I created this method to access the most recent grade for each test:
def last_grade
return reviews.find(:last).grade
end
This works fine for displaying the most recent grade in the test view, but how can I use it at the site level? Since the value is now in a method that's not stored in the database, I don't know how to work with it and can't find anything related to this at the major online tutorial/screencast sites.
Thanks in advance for your help!
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joins 方法允许访问 has_many :through 关联的属性。或者从所需的关联开始，系统会为您提供所需的连接。
来源：
The joins method allows access to the has_many :through association's attributes. Or start with the desired association, and the required joins are included for you.
sources: