Question

我有两个模型帖子和主题，它们具有一对多的关系

#Post.rb
class Post < ApplicationRecord
  belongs_to :topic
  validates :topic_id, presence: true
  validates :title, presence: true
  validates :body, presence: true
end

如果我通过调用Post.all来获得一系列帖子，例如

    #<ActiveRecord::Relation [#<Post id: 1, title: "Rails Code", body: "class TopicsController < ApplicationController\r\n  ...", created_at: "2018-05-22 09:34:15", updated_at: "2018-05-22 09:34:15", topic_id: "2">, 
#<Post id: 2, title: "Post with tags", body: "qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqq...", created_at: "2018-05-22 11:48:54", updated_at: "2018-05-22 11:48:54", topic_id: "2">, 
#<Post id: 3, title: "12hello world12", body: "12312sdfsdfsdsdsdsd31231231231231", created_at: "2018-05-23 12:54:02", updated_at: "2018-05-23 12:54:02", topic_id: "2">,
 #<Post id: 4, title: "12hello world12", body: "12312sdfsdfsdsdsdsd31231231231231", created_at: "2018-05-23 12:54:09", updated_at: "2018-05-23 12:54:09", topic_id: "1">,
 #<Post id: 5, title: "12hellsdssdo world12", body: "12312sdfsdfsdsdsdsd31231231231231", created_at: "2018-05-23 12:54:15", updated_at: "2018-05-23 12:54:15", topic_id: "1">]>

有没有办法可以按照topic_id对它们进行分组，这样我就可以按主题显示它们

示例

Topic - 1
post 1    post2   post 3
Topic -2
post4   post5

Answer 1

找到答案。你可以使用ruby的Enumerable#group_by：

来做到这一点

post.group_by{|post| post.topic_id}

Answer 2

使用此：

Post.all.group_by(&:topic_id).each do |topic_id, posts|
  ...
end

如何在哈希中基于id对ruby数组进行分组

2 个答案: