Resources

Source - https://github.com/driftingruby/127-active-record-tricks

Summary

user.rbclass User < ApplicationRecord
  belongs_to :status
  has_many :messages, dependent: :destroy
  scope :active, -> { joins(:status).merge(Status.active) }
  scope :unread_messages, -> { joins(:messages).merge(Message.unread) }
  default_scope { includes(:messages).unread_messages }
end

status.rbclass Status < ApplicationRecord
  has_many :users
  scope :active, -> { where(active: true) }
  # def self.active
  #   where(active: true)
  # end
end

message.rbclass Message < ApplicationRecord
  belongs_to :user
  scope :unread, -> { where(read: false)}
  scope :read, -> { where(read: true)}
end

Terminalrails db:create db:migrate db:seed
rails c

rails consoleUser.count
Status.count
Message.count

reload!

active_statuses = Status.where(active: true).pluck(:id)
active_users = User.where(status_id: active_statuses)
active_users = User.joins(:status).where(statuses: { active: true })

Status.active
Status.active.pluck(:id)
User.joins(:status).where(statuses: { id: Status.active.pluck(:id) })
User.joins(:status).merge(Status.active)

user = User.first
user.messages.pluck(:read)
user.messages.where(read: false)
user.messages.unread

User.active.joins(:messages).merge(Message.read)
User.active.unread_messages

User.active.scoping do
  User.last
end