Can't run method on scaffold index

Rails
1

I have this method to parse a url:

def parse_url

   elements = @article.url.split("/")
 if(elements[0] == "http:")
@home = elements[2]
  else
@home = elements[0]
 end

end

In the show method I can just use @home = parse_url and it works. In
the index I don’t know how to assign the proper id.
This is the index method:

def index

@articles = Article.paginate :page => params[:page], :per_page => 3


respond_to do |format|
  format.html # index.html.erb
  format.xml  { render :xml => @articles }
   end