代码之家 › 专栏 › 技术社区 › Sergey

rails3找到所有相关的记录有很多:通过

associations model ruby ruby-on-rails

7

Sergey · 技术社区 · 15 年前

我想列出所有与特定类别和课堂有关的帖子。

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

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

这确实是一个非常简单的任务,但我不知道我应该找什么(关键字)。

问题是一样的 this ,但在轨道上。

编辑 : 我给这个问题增加了更多细节。

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

4 回复 | 直到 8 年前

1

4

yfeldblum 15 年前

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

2

4

jbescoyez 11 年前

下面是我在Rails 3中要做的:

post.rb :

def self.in_category(category_id)
  if category_id.present?
    join(:category_posts).where(category_posts: {category_id: category_id})
  else
    self
  end
end

def self.in_classroom(classroom_id)
  if classroom_id.present?
    join(:classroom_posts).where(classroom_posts: {classroom_id: category_id})
  else
    self
  end
end

我不参加 Classroom 或 Category

现在,您可以:

Post.in_category(params[:category_id]).in_classroom(params[:classroom_id])

不过我还没有测试过。所以如果需要的话,不要犹豫。

3

2

Community CDub 8 年前

我认为这应该行得通:

Post.joins(:category_posts, :classroom_posts)
.where(
["category_posts.category_id = ? 
AND classroom_posts.classroom_id = ?", params[:category_id], params[:classroom_id]])

这将转换为如下SQL:

SELECT 
    p.*
FROM
    posts AS p
        INNER JOIN
    category_posts AS cap ON cap.id = p.category_posts_id
        INNER JOIN
    classroom_posts AS clp ON clpid = p.classroom_posts_id
WHERE
    cap.category_id = '1' AND clp.classroom_id = '1'
;

Post answer 在stackoverflow上。

4

0

Dan Healy 14 年前

if params[:category_id] && params[:classroom_id]
  Post.joins(:categories, :classrooms).where("classrooms.id" => params[:classroom_id], "categories.id" => params[:category_id]])
elsif params[:category_id]
  Category.find(params[:category_id]).posts
else
  Classroom.find(params[:classroom_id]).posts
end