[RUBY] Rails: How to write a rake task nicely

Good feeling = the following two points

  1. Easy to test
  1. (To some extent) the writing style can be unified among engineers




require_relative 'helpers/all_user_name_update_helper.rb'

namespace :issue_6885 do

  desc 'This is a sample'
  task all_user_name_update: :environment do
    helper = AllUserNameUpdateHelper.new



require_relative 'rake_helper_template'

class AllUserNameUpdateHelper < RakeHelperTemplate
  NEW_NAME = 'bar'

  def main
    template do |logger|
      all_users = get_all_user
      logger.info("Number of target users: #{all_users.size}")

      if all_users.blank?
        logger.info('The process ends because the number of target users was 0.')

      all_users.each { |user| update_name(user, NEW_NAME) }


  def get_all_user

  def update_name(user, new_name)
    user.update!(name: new_name)


class RakeHelperTemplate
  #Also performs standard output
  def make_logger(log_file_path)
    logger = ActiveSupport::Logger.new(log_file_path)
    stdout_logger = ActiveSupport::Logger.new(STDOUT)
    broadcast_logger = ActiveSupport::Logger.broadcast(stdout_logger)
    logger.formatter = Logger::Formatter.new

  #Make the log file name the same as the task name (replace it because it is better not to use a colon)
  #Cases called from other than the execution of the rake task (eg:spec) should be taken into consideration
  def make_log_file_path
    task_name = Rake.try(:application)&.top_level_tasks&.[](0)&.gsub(':','_') || Rails.env
    log_file_name = "#{task_name}.log"
    Rails.root.join('log', log_file_name)

  def template
    log_file_path = make_log_file_path

    #Be sure to dryrun unless you explicitly pass the string false
    is_dryrun = ENV['is_dryrun'] != 'false'

    logger = make_logger(log_file_path)
    logger.info("Start. is_dryrun: #{is_dryrun}")

    ActiveRecord::Base.transaction do
      raise ActiveRecord::Rollback if is_dryrun

    logger.info("Finish. log_file_path: #{log_file_path}")

Execution example

When making a dry run

$ is_dryrun=false bundle exec rake issue_6885:all_user_name_update
I, [2020-09-27T13:33:27.229764 #13040]  INFO -- : Start. is_dryrun: true
I, [2020-09-27T13:33:27.556890 #13040]  INFO -- :Number of target users: 1
I, [2020-09-27T13:33:27.755933 #13040]  INFO -- : Finish. log_file_path: /app/log/issue_6885_all_user_name_update.log 


  1. The .rake file only calls the helper class, rake's DSL? I tried to test the method of the class that I am accustomed to writing without worrying about the way of doing things
  1. Use yield to standardize dryrun and logger (part of) so that you don't have to define them every time you create a rake task.

Once you have a template, you can concentrate on what you want to do like all_user_name_update_helper.rb! (^ ○ ^)


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