after_commit.rb

after_commit.rb

# frozen_string_literal: true

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"

  git_source(:github) { |repo| "https://github.com/#{repo}.git" }

  # Activate the gem you are reporting the issue against.
  gem "activerecord", "5.2.0"
  gem "sqlite3", "~> 1.3.6"
end

require "active_record"
require "minitest/autorun"
require "logger"

# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :accounts, force: true do |t|
    t.string :first
    t.string :second
  end
end

class Account < ActiveRecord::Base
  after_commit :handle_after_commit, on: :update
  
  def handle_after_commit
    puts "after_commit: changes: #{previous_changes}"
  end
end

account_1 = Account.create!
account_2 = Account.create!

ActiveRecord::Base.transaction do
  account_1.update!(first: 'updating first on 1')
  account_1.update!(second: 'updating second on 1')
  account_2.update!(first: 'updating first on 2')
  account_2.update!(second: 'updating second on 2')
end

# result: 

# after_commit: changes: {"second"=>[nil, "updating second on 1"]}
# after_commit: changes: {"second"=>[nil, "updating second on 2"]}
#
# after_commit is triggered once at the end of transaction block
# be careful when using previous_changes inside of a transaction
# and when discrate operations matter