From: Ross Bamford <rossrt@...>
Date: 2006-02-23T02:06:57+09:00
Subject: Re: A small refractory problem

On Thu, 2006-02-23 at 01:18 +0900, James Byrne wrote:
> Ross Bamford wrote:
> > 
> > Maybe something like:
> > 
> > def move(sourcedir,globspec,targetdir,suf=nil)
> >   [sourcedir,targetdir].each do |dir|
> >     dir = File.expand_path(dir.to_s)
> >     raise ArgumentError, "#{dir} not valid" unless validpath?(sourcedir)
> >   end
> > end
> > 
> > Not sure how the rest of your code works, but it seems to me you could
> > have whatever class this is return 'path' from to_s, avoiding the check
> > you were doing (and avoiding having to set vars outside the block).
> > 
> > Hope that helps.
> 
> Yes, it does help, very much so.  The .move method is essentially 
> private, although not presently declared as such.  The intermediate 
> methods called from outside the instance are .get and .put which, on 
> reflection, are probably more suitable places to check the object class 
> of the passed directory arguments. That simplfies the assignments in the 
> move class as you recommend.

Well, glad to be able to help :)

I would just say though that I was actually advocating *not* checking
the arguments, but instead going for more of a duck-typing
implementation.

I'm assuming that the class you're working on looks something like this:

        class DirectoryThing
          def initialize(dir)
            @dir = dir
          end

          def move(sourcedir,globspec,targetdir,suf=nil)
            # .. code above
          end

          def path
            @dir
          end

          # ... etc ...
        end

And that you want to be able to pass strings, or other DirectoryThings,
as the arguments. So if you have:

        class DirectoryThing
          def to_s
            self.path
          end
        end

You can confidently to_s the argument you're passed (as above), rather
than having to explicitly check what it is - a string will give you
itself, while a DirectoryThing will give you it's path.

Just a thought...

-- 
Ross Bamford - rosco@roscopeco.REMOVE.co.uk