只需一次数据库调用即可将多个表中的数据存储在一个变量中（Rails）

Question

Assume these models:

class User < ActiveRecord::Base
  has_many :posts
end

class Post < ActiveRecord::Base
  belongs_to :user
  has_many :sections
end

class Section < ActiveRecord::Base
 belongs_to :post
 has_one :user, :through => :post
end

Assume this controller:

class SectionsController < ApplicationController
  def latest_sections
    @sections = Section.select(:name, :position, :updated_at)
                       .where(:public => true)
                       .order("updated_at DESC")
                       .limit(5)
  end
end

And finally this view:

<ul>
  <% @sections.each do |section| %>
    <li>
      <h1>Section updated on: <%= section.updated_at %></h1>
      <%= section.position %> - <%= section.name %>
      <% post = section.post; user = section.user %>
      From Post: <%= link_to post.name, post %>
      By User: <%= link_to user.username, user %>
    </li>
  <% end %>
</ul>

My problem:

This causes several database calls for the post and user variables I am declaring in the view for each cycle of the each loop.

Is there a way for me to include all and only the information I need for the code above to work with a single database call and store it in the @sections variable (I'm assuming this will work with a joins).

In order words, I want to store this information in the @sections variable in a single database call:

• section's name
• section's updated_at
• section's position
• section's user's username
• section's user's url_for
• section's post's name
• section's post's url_for

And how would I access this information?

(Note: none of this is specific to my case, it's just a generic example for a larger scenario)

Answer 1

在我看来，您正在询问包含选项。

Section.includes(:posts, :user).find(1)