From: Mark Volkmann <r.mark.volkmann@...>
Date: 2005-08-26T21:51:51+09:00
Subject: Re: symbols vs. strings

On 8/26/05, Brian Schr�der <ruby.brian@gmail.com> wrote:
> On 26/08/05, Mark Volkmann <r.mark.volkmann@gmail.com> wrote:
> > I got the impression that when a method expects a Hash containing
> > certain keys, I can generally specify the keys using either Symbol or
> > String objects. So I tried this.
> >
> > h = {}
> > h[:foo] = 19
> > h['foo'] = 20
> >
> > and was surprised to see that those are treated as distinct entries in the Hash.
> >
> > So how is it that I can sometimes choose whether I want to specify a
> > given key as either a Symbol or a String?
> >
> > For example, when using Tk and w represents some widget, I think I can
> > say either
> >
> > w.pack(:side => 'top')
> >
> > or
> >
> > w.pack('side' => 'top')
 
> That can e.g. be implemented like this:
> 
> def pack(arghash)
>   arghash = arghash.inject({}) { | r, (k, v) | r[k.to_s] = v; r }
>   side = arghash['side']
>   ...
> end

Just to clarify, are you saying that ...

1) If I want my code that accepts a Hash parameter to allow keys to be
either Symbols or Strings, I need to use an approach like you showed
above.

2) Many existing Ruby classes do this.

-- 
R. Mark Volkmann
Partner, Object Computing, Inc.