Rails 3找到所有相关记录has_many:through

Question

我想列出与某个特定类别和课堂相关的所有帖子.

我有:

class Post < ActiveRecord::Base
  has_many :category_posts
  has_many :categories, :through => :category_posts
  has_many :classroom_posts
  has_many :classrooms, :through => :classroom_posts
end

class Category < ActiveRecord::Base
  has_many :category_posts
  has_many :posts, :through => :category_posts
end

class CategoryPost < ActiveRecord::Base
  belongs_to :category
  belongs_to :post
end

class Classroom < ActiveRecord::Base
  has_many :classroom_posts
  has_many :posts, :through => :classroom_posts
end

class ClassroomPost < ActiveRecord::Base
  belongs_to :classroom
  belongs_to :post
end

我想做这样的事情

Post.where(["category.id = ? AND classroom.id = ?", params[:category_id], params[:classroom_id]])

这确实是非常简单的任务,但我不知道我应该寻找什么(关键字).

这就像同样的问题,这个,但是在轨道上.

编辑:我在问题中添加了更多细节.这有效,但前提是我指定了两个参数.女巫并非总是如此 - 我不知道会指定什么样的参数.

Post.joins(:categories, :classrooms).where(["categories.id = ? AND classrooms.id = ?", params[:classroom_id], params[:category_id]])

Answer 1

Category.find(params[:category_id]).posts

另请查看指南：

• Rails 2.35 指南
• Rails 3.0 指南