zhandao

module HavingAssoc
  extend ActiveSupport::Concern

  class_methods do
    # @example
    #   Child.missing_assoc(:lessons)
    #   Child.missing_assoc(:lessons).size                      # => children's count
    #   Child.missing_assoc(:lessons, filter: Lesson.finished)  # => [children]
    def missing_assoc(assoc_name, filter: nil)
      if filter.nil?

zhandao

Jsonb Query Scopes

Based on [https://github.com/DmitryTsepelev/store_model]

module JsonbQuery
  extend ActiveSupport::Concern

  included do
    # where_jsonb(:info, { name: "John", age: 18..28, date: "< 2020-01-01" })
    scope :where_jsonb, -> (column_name, attributes) do

zhandao

Find histories

# separate history file into current project
Pry.config.history_file = ".pry_history"

# @usage
#   hist User.first
#   hist User.first 3
#   hist User.first 3 5

zhandao

inspired by [https://sourcediving.com/this-rails-cache-is-not-your-friend-512871c138aa]

Let ActiveRecord take record instance directly from memory (cached), instead of instantiate from result set, for reducing memory allocation times and time.

It is very simple implementation of Identity Map.

It is suitable for reading is much more frequent than updating, like hot posts (preferably non editable).

zhandao

des to be written.

class User < ApplicationRecord
  def self.select_tag = all.select { _1.tags.present? }

  relation_delegate_class(ActiveRecord::Relation).class_eval do
    def select_age = select { _1.age in ..18 }
    def find_loaded_by(**) = find { my_match?(_1, **) }
 end