rails-generators
Create expert-level Ruby on Rails generators for models, services, controllers, and full-stack features. Use when building custom generators, scaffolds, or code generation tools for Rails applications, or when the user mentions Rails generators, Thor DSL, or automated code generation.
Resources
1Install
npx skillscat add el-feo/ai-context/rails-generators Install via the SkillsCat registry.
SKILL.md
Build production-ready Rails generators that automate repetitive coding tasks and enforce architectural patterns. This skill covers creating custom generators for models, service objects, API scaffolds, and complete features with migrations, tests, and documentation.
Create a simple service object generator:
# lib/generators/service/service_generator.rb
module Generators
class ServiceGenerator < Rails::Generators::NamedBase
source_root File.expand_path('templates', __dir__)
def create_service_file
template 'service.rb.tt', "app/services/#{file_name}_service.rb"
end
def create_service_test
template 'service_test.rb.tt', "test/services/#{file_name}_service_test.rb"
end
end
endTemplate file (templates/service.rb.tt):
class <%= class_name %>Service
def initialize
end
def call
# Implementation goes here
end
endInvoke with: rails generate service payment_processor
</basic_generator>
- Enforce architectural patterns: Service objects, form objects, presenters, query objects
- Reduce boilerplate: API controllers with standard CRUD, serializers, policy objects
- Maintain consistency: Team conventions for file structure, naming, and organization
- Automate complex setup: Multi-file features with migrations, tests, and documentation
- Override Rails defaults: Customize scaffold behavior for your application's needs</when_to_create>
Study Rails 8 built-in generators for current best practices.
</rails_8_updates>
Rails::Generators::Base: Simple generators without required argumentsRails::Generators::NamedBase: Generators requiring a name argument
class ServiceGenerator < Rails::Generators::NamedBase
# Automatically provides: name, class_name, file_name, plural_name
endsource_root File.expand_path('templates', __dir__)
class_option :namespace, type: :string, default: nil, desc: "Namespace for the service"
class_option :skip_tests, type: :boolean, default: false, desc: "Skip test files"Access options with: options[:namespace]
</step_2>
def create_service_file
template 'service.rb.tt', service_file_path
end
def create_test_file
return if options[:skip_tests]
template 'service_test.rb.tt', test_file_path
end
private
def service_file_path
if options[:namespace]
"app/services/#{options[:namespace]}/#{file_name}_service.rb"
else
"app/services/#{file_name}_service.rb"
end
end<% if options[:namespace] -%>
module <%= options[:namespace].camelize %>
class <%= class_name %>Service
def call
# Implementation
end
end
end
<% else -%>
class <%= class_name %>Service
def call
# Implementation
end
end
<% end -%>Important: Use <%% to output literal <% in generated files.
</step_4>
rails generate service payment_processor --namespace=billing
rails generate service notifier --skip-testsclass CustomModelGenerator < Rails::Generators::NamedBase
source_root File.expand_path('templates', __dir__)
class_option :parent, type: :string, desc: "Parent model for belongs_to"
class_option :scope, type: :array, desc: "Scopes to generate"
def create_migration
migration_template 'migration.rb.tt',
"db/migrate/create_#{table_name}.rb"
end
def create_model_file
template 'model.rb.tt', "app/models/#{file_name}.rb"
end
def create_test_file
template 'model_test.rb.tt', "test/models/#{file_name}_test.rb"
end
endSee references/model-generator.md for complete example.
</model_generator>
class ServiceGenerator < Rails::Generators::NamedBase
source_root File.expand_path('templates', __dir__)
class_option :result_object, type: :boolean, default: true
def create_service
template 'service.rb.tt', "app/services/#{file_name}_service.rb"
end
def create_result_object
return unless options[:result_object]
template 'result.rb.tt', "app/services/#{file_name}_result.rb"
end
endSee references/service-generator.md for complete example.
</service_object_generator>
class ApiControllerGenerator < Rails::Generators::NamedBase
source_root File.expand_path('templates', __dir__)
class_option :serializer, type: :string, default: 'active_model_serializers'
class_option :actions, type: :array, default: %w[index show create update destroy]
def create_controller
template 'controller.rb.tt',
"app/controllers/api/v1/#{file_name.pluralize}_controller.rb"
end
def create_serializer
template "serializer_#{options[:serializer]}.rb.tt",
"app/serializers/#{file_name}_serializer.rb"
end
def add_routes
route "namespace :api do\n namespace :v1 do\n resources :#{file_name.pluralize}\n end\n end"
end
endSee references/api-generator.md for complete example.
</api_controller_generator>
class FeatureGenerator < Rails::Generators::NamedBase
source_root File.expand_path('templates', __dir__)
class_option :api, type: :boolean, default: false
def create_model
invoke 'model', [name], migration: true
end
def create_controller
if options[:api]
invoke 'api_controller', [name]
else
invoke 'controller', [name], actions: %w[index show new create edit update destroy]
end
end
def create_views
return if options[:api]
%w[index show new edit _form].each do |view|
template "views/#{view}.html.erb.tt",
"app/views/#{file_name.pluralize}/#{view}.html.erb"
end
end
def create_tests
invoke 'test_unit:model', [name]
invoke 'test_unit:controller', [name]
invoke 'test_unit:system', [name] unless options[:api]
end
endSee references/scaffold-generator.md for complete example.
</full_stack_scaffold>
</common_patterns>
class ServiceGenerator < Rails::Generators::NamedBase
hook_for :test_framework, as: :service
endThis automatically invokes test_unit:service or rspec:service based on configuration.
Creating hook responders:
# lib/generators/rspec/service/service_generator.rb
module Rspec
module Generators
class ServiceGenerator < Rails::Generators::NamedBase
source_root File.expand_path('templates', __dir__)
def create_service_spec
template 'service_spec.rb.tt',
"spec/services/#{file_name}_service_spec.rb"
end
end
end
endSee references/hooks.md for hook patterns and fallback configuration.
def create_dependencies
invoke 'model', [name], migration: true
invoke 'service', ["#{name}_processor"]
invoke 'serializer', [name]
endConditional invocation:
def create_optional_files
invoke 'mailer', [name] if options[:mailer]
invoke 'job', ["#{name}_job"] if options[:background_job]
end# lib/generators/admin/resource/resource_generator.rb
module Admin
module Generators
class ResourceGenerator < Rails::Generators::NamedBase
source_root File.expand_path('templates', __dir__)
def create_admin_resource
template 'resource.rb.tt',
"app/admin/#{file_name}.rb"
end
end
end
endInvoke with: rails generate admin:resource User
Generator search path:
rails/generators/[name]/[name]_generator.rbgenerators/[name]/[name]_generator.rbrails/generators/[name]_generator.rbgenerators/[name]_generator.rb
See references/namespacing.md for fallback patterns.
# Create files
create_file 'config/settings.yml', yaml_content
copy_file 'template.rb', 'config/template.rb'
template 'config.rb.tt', 'config/settings.rb'
# Modify existing files
insert_into_file 'config/routes.rb', route_content, after: "Rails.application.routes.draw do\n"
gsub_file 'config/application.rb', /old_value/, 'new_value'
comment_lines 'config/environments/production.rb', /config.assets.compile/
# Directory operations
empty_directory 'app/services'
directory 'templates/views', 'app/views/admin'
# Rails-specific helpers
initializer 'service_config.rb', config_content
lib 'custom_validator.rb', validator_content
rakefile 'import_tasks.rake', rake_content
route "namespace :api do\n resources :users\n end"See references/file-actions.md for complete reference.
</file_manipulation>
Categories
Install
npx skillscat add el-feo/ai-context/rails-generators Install via the SkillsCat registry.