Modify existing files with a rails generator?

Question

I'm writing a generator that adds a few files that my server will use. I'd also like to add a line to the environment.rb file. Can this be done with a generator or should I be using an app template?

Answer 1

Rather than modifying environment.rb, check out what you can do with Rails initializers. Basically, you're just going to create a new Ruby .rb file within config/initializers and keep your configuration loading code in there. If you need per-environment configuration, it's best to create another (usually YAML) file within config/ that will store the per-environment configuration variables and load that YAML in your initializer.

Answer 2

You can use initializers for custom initialization code, but if you find adding to an existing file with a generator is appropriate here's how the built-in generators do it:

# Excerpted from template_runner.rb

# Make an entry in Rails routing file conifg/routes.rb 
def route(routing_code)
  log 'route', routing_code
  sentinel = 'ActionController::Routing::Routes.draw do |map|'

  in_root do
    gsub_file 'config/routes.rb', /(#{Regexp.escape(sentinel)})/mi do |match|
      "#{match}\n  #{routing_code}\n"
    end
  end
end

As you can see, it's just figuring out where they want the code to go (the sentinal line) and stuffing the new line in right after it.