帮助Rails find_by查询

Say if @news_writers is an array of records. I then want to use @news_writers to find all news items that are written by all the news writers contained in @news_writers.

假设@news_writers是一个记录数组。然后,我想使用@news_writers查找由@news_writers中包含的所有新闻作者编写的所有新闻项目。

So I want something like this (but this is syntactically incorrect):

所以我想要这样的东西(但这在语法上是不正确的):

@news = News.find_all_by_role_id(@news_writers.id)

Note that

class Role < ActiveRecord::Base
  has_many :news
end

and 

class News < ActiveRecord::Base
  belongs_to :role
end

2 个解决方案

#1

Like ennen, I'm unsure what relationships your models are supposed to have. But in general, you can find all models with a column value from a given set like this:

和ennen一样,我不确定你的模型应该有什么样的关系。但一般来说,您可以找到具有给定集合中列值的所有模型,如下所示:

  News.all(:conditions => {:role_id => @news_writers.map(&:id)})

This will create a SQL query with a where condition like:

这将创建一个SQL查询,其中where条件如下:

  WHERE role_id IN (1, 10, 13, ...)

where the integers are the ids of the @news_writers.

其中整数是@news_writers的id。

#2

I'm not sure if I understand you - @news_writers is a collection of Role models? If that assumption is correct, your association appears to be backwards - if these represent authors of news items, shouldn't News belong_to Role (being the author)?

我不确定我是否理解你 - @news_writers是一个角色模型的集合?如果这个假设是正确的,那么你的关联似乎是倒退 - 如果这些代表新闻项目的作者,那么新闻属于哪个角色(作为作者)?

At any rate, I would assume the most direct approach would be to use an iterator over @news_writers, calling on the association for each news_writer (like news_writer.news) in turn and pushing it into a separate variable.

无论如何,我认为最直接的方法是在@news_writers上使用迭代器,依次调用每个news_writer(如news_writer.news)的关联并将其推送到一个单独的变量中。

Edit: Daniel Lucraft's suggestion is a much more elegant solution than the above.

编辑:Daniel Lucraft的建议是比上述更优雅的解决方案。

#1