Rails5如何使用ActiveRecord Relation对象构建提要

Question

I'd like to build a feed with Microposts:

First I collect all Microposts from my following with visible_for 'following'

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)

Then I collect all Microposts from my following (AND status "contact") with 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)

Is there any way to get following_feed and contacts_feed together? that I can write:

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

In other words: global_feed should contain all Microposts from users the current user follows with visible_for 'followers'
+ all Microposts from users the curent user follows with status 'contact' with visible_for 'contacts'

Update:

Relationship

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

User

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

Micropost

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 is a method only available on ActiveRecord relations. Which means you will need to select the data you need in one query.

So if I'm reading your sample correctly, you want all Micropost s from users the current user follows that are visible for contacts or following .

You can select them in one query like so

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))