ActsAsRenderer Brings Output to Models

Judging by the fact that there are several posts about this topic out in the wild, and that I have come across a need for it more than once, I thought it would be helpful to wrap up this functionality into a plugin and put it out into the world. Give a warm welcome to ActsAsRenderer!

Before you go off on a tirade about the evils of violating MVC, let me first say I know the arguments and I agree with you. However, in a world of complex systems where not everything is done via full-stack HTTP, there are legitimate reasons to output data directly from models, and ActsAsRenderer helps you do it.

With ActsAsRenderer, you get four cool new functions.

For your model class, you get render_file and render_string. For your instances, you get render_to_file and render_to_string.

Probably the most common (and legitimate) use of this kind of functionality is for rendering data out of a Rails script (say with script/runner). Since that environment is not a full-stack HTTP view of the world, it's a real pain to render any kind of structured output. Not anymore! With acts_as_renderer in your model, you can render your views and give your model the voice it's been lacking!

I've had this need come up several times. Most recently, I built a server configuration management system using Rails. While it is nice to preview the rendered configuration files using Rails-over-HTTP, it is also essential to be able to write those same configuration files out to the filesystem. In another case, I had a background DRb process that needed to be able to render templated output to the filesystem. I had to go build a mock-controller and do some pretty unsavory things; all of that would have been obviated with acts_as_renderer.

Now, I can simply say:

class Server < ActiveRecord::Base
  acts_as_renderer
  
  def build_configuration
    CLIENT_CONFIG_FILES.each do |f|
      render_to_file("configs/#{f}", "#{config_dir}/#{f}.conf")
    end
  end
end

The render_to_file function renders the templates located in configs (under app/views by default) and writes them to the files specified in the config_dir; it's also smart enough to know that render_to_file is being called from a 'server' instance and sets @server accordingly. So my templates in configs are simply:

; Configuration Snippet for Server <%=@server.description%>

<%= render :partial => 'configs/queue', :collection => @server.queues %>

Please do think before using this plugin. It can be used for some seriously evil violations of good MVC design practice, and you are responsible for your own actions. However, this can also be used to make your existing designs *much* more robust and elegant, and I encourage you to use it where that is true.

It's ready to drop in. Everything is there, including tests. Enjoy!

NOTE: Version 1.0 only supported Rails 2.0; I just added version 1.01 which will work with either Rails 1.2.x or 2.0.x. Please feel free to ping me with any questions.

acts_as_renderer at RubyForge