Rails5 如何使用 ActiveRecord 关系对象构建提要

Question

我想用微博建立一个提要：

首先我从我的关注者visible_for 'following'

收集所有微博

following_ids_subselect = "SELECT followed_id FROM relationships
                           WHERE  follower_id = :user_id"
following_feed = Micropost.where("visible_for = 'following' 
                                   AND user_id IN (#{following_ids_subselect})", user_id: id)

然后我从我的关注者（和状态 "contact"）收集所有微博 visible_for 'contact'

contacts_ids_subselect = "SELECT followed_id FROM relationships
                          WHERE  follower_id = :user_id
                          AND status = 'contact'"
contacts_feed = Micropost.where("visible_for = 'contacts' 
                                   AND user_id IN (#{contacts_ids_subselect})", user_id: id)

有什么方法可以让 following_feed 和 contacts_feed 在一起吗？我可以写：

@feed_items = global_feed.paginate(page: params[:page])

换句话说： global_feed 应包含当前用户关注 visible_for 'followers'
的所有微博 + 当前用户关注status 'contact'和visible_for 'contacts'

的所有微博

更新：

关系

class Relationship < ApplicationRecord
# Table name: relationships
#
#  id           :integer(4)      not null, primary key
#  follower_id  :integer(4)
#  followed_id  :integer(4)
#  status       :string        

  belongs_to :follower, class_name: "User"
  belongs_to :followed, class_name: "User"
end

用户

class User < ApplicationRecord
  has_many :active_relationships, class_name:  "Relationship",
                              foreign_key: "follower_id",
                              dependent:   :destroy
  has_many :following, through: :active_relationships, source: :followed
  has_many :passive_relationships, class_name:  "Relationship",
                               foreign_key: "followed_id",
                               dependent:   :destroy
  has_many :followers, through: :passive_relationships, source: :follower
  (..)
end

微博

class Micropost < ApplicationRecord
#
# Table name: microposts
#
#  id          :integer(4)      not null, primary key
#  user_id     :integer(4)
#  content     :string
#  visible_for :string   

  belongs_to :user
  default_scope -> { order('created_at DESC') }     
end

Answer 1

#paginate 是一种仅适用于 ActiveRecord 关系的方法。这意味着您将需要 select 在一次查询中获得所需的数据。

因此，如果我正确阅读了您的样本，您希望当前用户关注的用户的所有 Micropost 对 contacts 或 following 可见。

您可以像这样 select 在一个查询中使用它们

following_user_ids = user.following.pluck(:id)
contact_user_ids = Relationship.where(status: "contact", follower_id: user.id).pluck(:follower_id)

Microposts.where("(visible_for = 'followers' and user_id in (?)) OR (visible_for = "contacts" and user_id in (?)"), following_user_ids, contact_user_ids))

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