Generator scripts handle command-line invocation. Each script responds to an invoke! class method which handles option parsing and generator invocation.

Methods
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R
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Included Modules
Instance Public methods
run(args = [], runtime_options = {})

Run the generator script. Takes an array of unparsed arguments and a hash of parsed arguments, takes the generator as an option or first remaining argument, and invokes the requested command.

Source: show 

# File rails/railties/lib/rails_generator/scripts.rb, line 17
def run(args = [], runtime_options = {})
  begin
    parse!(args.dup, runtime_options)
  rescue OptionParser::InvalidOption => e
    # Don't cry, script. Generators want what you think is invalid.
  end

  # Generator name is the only required option.
  unless options[:generator]
    usage if args.empty?
    options[:generator] ||= args.shift
  end

  # Look up generator instance and invoke command on it.
  Rails::Generator::Base.instance(options[:generator], args, options).command(options[:command]).invoke!
rescue => e
  puts e
  puts "  #{e.backtrace.join("\n  ")}\n" if options[:backtrace]
  raise SystemExit
end
Instance Protected methods
banner()

Override with your own script usage banner.

Source: show 

# File rails/railties/lib/rails_generator/scripts.rb, line 40
def banner
  "Usage: #{$0} generator [options] [args]"
end
usage_message()

Source: show 

# File rails/railties/lib/rails_generator/scripts.rb, line 44
          def usage_message
            usage = "\nInstalled Generators\n"
            Rails::Generator::Base.sources.each do |source|
              label = source.label.to_s.capitalize
              names = source.names
              usage << "  #{label}: #{names.join(', ')}\n" unless names.empty?
            end

            usage << "
More are available at http://rubyonrails.org/show/Generators
  1. Download, for example, login_generator.zip
  2. Unzip to directory #{Dir.user_home}/.rails/generators/login
     to use the generator with all your Rails apps
"

            if Object.const_defined?(:RAILS_ROOT)
              usage << "     or to #{File.expand_path(RAILS_ROOT)}/generators/login
     to use with this app only.
"
            end

            usage << "  3. Run generate with no arguments for usage information
       #{$0} login

Generator gems are also available:
  1. gem search -r generator
  2. gem install login_generator
  3. #{$0} login

"
            return usage
          end