The application builder allows you to override elements of the application generator without being forced to reverse the operations of the default generator.

This allows you to override entire operations, like the creation of the Gemfile, README, or JavaScript files, without needing to know exactly what those operations do so you can create another template action.

class CustomAppBuilder < Rails::AppBuilder
  def test
    @generator.gem "rspec-rails", group: [:development, :test]
    run "bundle install"
    generate "rspec:install"
  end
end
Methods
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Instance Public methods
app()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 80
def app
  directory "app"

  keep_file "app/assets/images"
  empty_directory_with_keep_file "app/assets/javascripts/channels" unless options[:skip_action_cable]

  keep_file  "app/controllers/concerns"
  keep_file  "app/models/concerns"
end
bin()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 90
def bin
  directory "bin" do |content|
    "#{shebang}\n" + content
  end
  chmod "bin", 0755 & ~File.umask, verbose: false
end
bin_when_updating()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 97
def bin_when_updating
  bin_yarn_exist = File.exist?("bin/yarn")

  bin

  if options[:api] && !bin_yarn_exist
    remove_file "bin/yarn"
  end
end
config()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 107
def config
  empty_directory "config"

  inside "config" do
    template "routes.rb"
    template "application.rb"
    template "environment.rb"
    template "cable.yml" unless options[:skip_action_cable]
    template "puma.rb"   unless options[:skip_puma]
    template "spring.rb" if spring_install?
    template "storage.yml" unless skip_active_storage?

    directory "environments"
    directory "initializers"
    directory "locales"
  end
end
config_target_version()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 243
def config_target_version
  defined?(@config_target_version) ? @config_target_version : Rails::VERSION::STRING.to_f
end
config_when_updating()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 125
def config_when_updating
  cookie_serializer_config_exist = File.exist?("config/initializers/cookies_serializer.rb")
  action_cable_config_exist      = File.exist?("config/cable.yml")
  active_storage_config_exist    = File.exist?("config/storage.yml")
  rack_cors_config_exist         = File.exist?("config/initializers/cors.rb")
  assets_config_exist            = File.exist?("config/initializers/assets.rb")
  csp_config_exist               = File.exist?("config/initializers/content_security_policy.rb")

  @config_target_version = Rails.application.config.loaded_config_version || "5.0"

  config

  unless cookie_serializer_config_exist
    gsub_file "config/initializers/cookies_serializer.rb", /json(?!,)/, "marshal"
  end

  if !options[:skip_action_cable] && !action_cable_config_exist
    template "config/cable.yml"
  end

  if !skip_active_storage? && !active_storage_config_exist
    template "config/storage.yml"
  end

  if options[:skip_sprockets] && !assets_config_exist
    remove_file "config/initializers/assets.rb"
  end

  unless rack_cors_config_exist
    remove_file "config/initializers/cors.rb"
  end

  if options[:api]
    unless cookie_serializer_config_exist
      remove_file "config/initializers/cookies_serializer.rb"
    end

    unless assets_config_exist
      remove_file "config/initializers/assets.rb"
    end

    unless csp_config_exist
      remove_file "config/initializers/content_security_policy.rb"
    end
  end
end
configru()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 62
def configru
  template "config.ru"
end
credentials()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 181
def credentials
  return if options[:pretend] || options[:dummy_app]

  require "rails/generators/rails/credentials/credentials_generator"
  Rails::Generators::CredentialsGenerator.new([], quiet: options[:quiet]).add_credentials_file_silently
end
database_yml()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 188
def database_yml
  template "config/databases/#{options[:database]}.yml", "config/database.yml"
end
db()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 192
def db
  directory "db"
end
gemfile()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 58
def gemfile
  template "Gemfile"
end
gitignore()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 66
def gitignore
  template "gitignore", ".gitignore"
end
lib()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 196
def lib
  empty_directory "lib"
  empty_directory_with_keep_file "lib/tasks"
  empty_directory_with_keep_file "lib/assets"
end
log()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 202
def log
  empty_directory_with_keep_file "log"
end
master_key()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 172
def master_key
  return if options[:pretend] || options[:dummy_app]

  require "rails/generators/rails/master_key/master_key_generator"
  master_key_generator = Rails::Generators::MasterKeyGenerator.new([], quiet: options[:quiet], force: options[:force])
  master_key_generator.add_master_key_file_silently
  master_key_generator.ignore_master_key_file_silently
end
package_json()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 76
def package_json
  template "package.json"
end
public_directory()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 206
def public_directory
  directory "public", "public", recursive: false
end
rakefile()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 46
def rakefile
  template "Rakefile"
end
readme()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 50
def readme
  copy_file "README.md", "README.md"
end
ruby_version()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 54
def ruby_version
  template "ruby-version", ".ruby-version"
end
storage()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 210
def storage
  empty_directory_with_keep_file "storage"
  empty_directory_with_keep_file "tmp/storage"
end
system_test()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 227
def system_test
  empty_directory_with_keep_file "test/system"

  template "test/application_system_test_case.rb"
end
test()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 215
def test
  empty_directory_with_keep_file "test/fixtures"
  empty_directory_with_keep_file "test/fixtures/files"
  empty_directory_with_keep_file "test/controllers"
  empty_directory_with_keep_file "test/mailers"
  empty_directory_with_keep_file "test/models"
  empty_directory_with_keep_file "test/helpers"
  empty_directory_with_keep_file "test/integration"

  template "test/test_helper.rb"
end
tmp()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 233
def tmp
  empty_directory_with_keep_file "tmp"
  empty_directory "tmp/cache"
  empty_directory "tmp/cache/assets"
end
vendor()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 239
def vendor
  empty_directory_with_keep_file "vendor"
end
version_control()
# File rails/railties/lib/rails/generators/rails/app/app_generator.rb, line 70
def version_control
  if !options[:skip_git] && !options[:pretend]
    run "git init", capture: options[:quiet]
  end
end