具有复合主键的 Rails 3.1 嵌套资源 (id +parent_id)

发布于 2024-12-20 18:36:59 字数 508 浏览 3 评论 0原文

假设我需要嵌套在routes.rb中的两个资源，如下所示：

resources :post do
  resources :comment
end

按照约定，comments.id将是评论主键和comments.post_id 将是外键。

我需要将主键作为复合键[comments.post_id, comments.id]。

这样我就可以拥有每个不同帖子的第一个评论，id == 1，每个不同帖子的第二个评论，id == 2，依此类推...

当然，我还需要禁用引用评论的每个路由（子资源），而不同时引用其帖子（父资源）。

这只是一个例子，我的实际项目不是关于博客的（我以不同的方式处理这个问题），我想知道是否有一种方法可以实现嵌套资源的这种行为以实现兼容性与遗留数据库。

谢谢。

原文

Let's assume I need two resources nested in the routes.rb as follows:

resources :post do
  resources :comment
end

By convention comments.id will be the comments primary key and comments.post_id will be a foreign key.

I need the primary key to be the composite key [comments.post_id, comments.id].

So that I could have every first comment of each distinct post with id == 1, every second comment of each distinct post with id == 2 and so on...

Of course I also need to disable every route that refers to a comment (the child resource) without referring also to its post (the parent resource).

This is just an example, my actual project isn't about a blog (I'd handled this problem differently), I'd like to know if there is a way to achieve such a behavior for a nested resource in order to achieve compatibility with a legacy database.

Thank you.

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我最亲爱的 2024-12-27 18:36:59

一种方法是创建另一列（保留 posts.id 作为主键），在该列上添加唯一性验证，其范围为帖子 id，然后在 _create hood 之前或之后写入一些内容以生成该列值。

一个示例（不是真正的代码）

class Comment < ActiveRecord::Base
  ...
  validates_uniqueness_of :sub_id, :scope => :post_id

  before_create do
    this.sub_id = post.comments.size + 1
  end
end

因此 sub_id 列充当主键。当您查询某个帖子的评论时，您可以执行以下操作：

post.comments.where(:sub_id => val).first

或

post.comments.find_by_sub_id(val)

请注意，应调整此处的实际逻辑以满足您的要求。例如，如果可以删除评论，那么在帖子上保留一个计数器可能是个好主意，该计数器将用于确定下一个 sub_id （或编写一个 sub id 生成器类）。

One way to do this is by creating another column (leave the posts.id as it was primary key), add an uniqueness validation on that column with scope to the post id, then write some before or after _create hood to generate that column value.

An example (not real code)

class Comment < ActiveRecord::Base
  ...
  validates_uniqueness_of :sub_id, :scope => :post_id

  before_create do
    this.sub_id = post.comments.size + 1
  end
end

So the sub_id column acts as a primary key. When you query a comment for a certain post, you do this:

post.comments.where(:sub_id => val).first

post.comments.find_by_sub_id(val)

Please be noted the real logic here should be adjusted to satisfy your requirement. For instance, if comments can be deleted, it might be a good idea to keep an counter on post which will used to determine the next sub_id (or write a sub id generator class).

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