From: benjohn@...
Date: 2006-10-04T22:13:56+09:00
Subject: Re: How to DRY this?

> Hello,
>
> I have two very similar code snippets in two different methods, and I am
> absolutely sure there is some nice way to DRY them in Ruby... I am still
> a noob when comes to Ruby idioms so I'd appreciate some help ;-)
>
>      ...
>      while element.class != Hpricot::Doc do
>          path.push element.name
>          element = element.parent
>      end
>      ...
>
> and
>      ...
>      while element.class != Hpricot::Doc do
>          path.push element
>          element = element.parent
>      end
>      ...

Pull out the loop logic in to another method...

def traverse_up(element)
  while element.class != Hpricot::Doc do
    yield(element)
    element = element.parent
  end
end

The two cases now become:
  traverse_up(element) {|e| path.push e,name}
and
  traverse_up(element) {|e| path.push e}


Additional comments:

It may (or may not) make sense for the traverse_up method to be a member
of element's class.

You might like to provide an additional, optional argument, that can be
used to control loop termination...

def traverse_up(element, terminate_at = Hpricot::Doc)
  while !(terminate_at === element) do
    yield(element)
    element = element.parent
  end
end

(I've also changed the way that element's class is checked here - but
classes of Hpricot::Doc will also match and terminate the loop).

Cheers,
  Benj