Lets say you want to be able to arbitrarily see the value of a variable in your controller action without going into the debugger or changing your templates. What if you just passed some ruby code in the url?

asdfs_controller.rb

 def show
    @asdf = Asdf.find(params[:id])
    if (params[:ruby])
      return( render :text => eval(params[:ruby]) )
    end

    respond_to do |format|

      format.html # show.html.erb

      format.xml  { render :xml => @asdf }

    end

  end

Then you could put in your url things like:

http://0.0.0.0:3000/asdfs/1?ruby=@asdf.name

http://0.0.0.0:3000/asdfs/1?ruby=@asdf.class

http://0.0.0.0:3000/asdfs/1?ruby=self.inspect

http://0.0.0.0:3000/asdfs/1?ruby=Asdf.find(:all).size.to_s