Using ActiveRecord in a Rake-based application

application.rb

# config/application.rb

RAKE_PATH = File.expand_path(".")
RAKE_ENV  = ENV.fetch("RAKE_ENV", "development")

Bundler.require :default, RAKE_ENV

# Configuration for ActiveRecord rake tasks
ActiveRecord::Tasks::DatabaseTasks.root             = RAKE_PATH
ActiveRecord::Tasks::DatabaseTasks.env              = RAKE_ENV
ActiveRecord::Tasks::DatabaseTasks.db_dir           = "db"
ActiveRecord::Tasks::DatabaseTasks.migrations_paths = ["db/migrate"]
ActiveRecord::Tasks::DatabaseTasks.seed_loader      = nil

# Set up ActiveRecord database connection
ActiveRecord::Base.configurations = YAML.load_file("config/database.yml")
ActiveRecord::Base.establish_connection RAKE_ENV.to_sym

# Add local lib directory to the load path
$LOAD_PATH.unshift File.join(RAKE_PATH, "lib")

database.yml

# config/database.yml

development:
  adapter: postgresql
  database: my_app_development

test:
  adapter: postgresql
  database: my_app_test

Rakefile

require "bundler/setup"

load "active_record/railties/databases.rake"

task :environment do
  require "./config/application"

  require "my_app"
end

task :console => :environment do
  require "irb"

  ARGV.clear
  IRB.start
end