2008/3/13, Trans <transfire / gmail.com>:
>
>
>  On Mar 13, 4:42 am, "Robert Klemme" <shortcut... / googlemail.com>
>  wrote:
>  > 2008/3/13, Trans <transf... / gmail.com>:
>
> >
>  > > Which approach is better: parametric module or an injecting class
>  > >  method.
>  >
>  > Are you writing a book on best practices?  There seem to be quite a
>  > few of these questions recently. :-))
>
>
> Ha... I probably should be! But right now I'm just working through
>  some old "TODO" questions in Facets.

LOL

>  > >   # Generates identity/key methods based on specified attributes.
>  > >   #
>  > >   #   equate_on :a, :b
>  > >   #
>  > >   # _is equivalent to_
>  > >   #
>  > >   #   def ==(o)
>  > >   #     self.a == o.a && self.b == o.b
>  > >   #   end
>  > >   #
>  > >   #   def eql?(o)
>  > >   #     self.a.eql?(o.a) && self.b.eql?(o.b)
>  > >   #   end
>  > >   #
>  > >   #   def hash()
>  > >   #     self.a.hash ^ self.b.hash
>  > >   #   end
>  >
>  > >   def equate_on(*fields)
>  > >     code = ""
>  > >     code << "def ==(o) "   << fields.map {|f| "self.#{f} ==
>  > >  o.#{f}" }.join(" && ")    << " end\n"
>  > >     code << "def eql?(o) " << fields.map {|f| "self.#{f}.eql?
>  > >  (o.#{f})" }.join(" && ") << " end\n"
>  > >     code << "def hash() "  << fields.map {|f|
>  > >  "self.#{f}.hash" }.join(" ^ ")          << " end\n"
>  > >     class_eval( code )
>  > >     fields
>  > >   end
>  >
>  > I opt for the second solution because the anonymous module does not
>  > have any reuse effects - unless you cache it based on field names. :-)
>
>
> :) And if we do cache based on field names?

Aw, com' on.  Interesting additional question: should order matter?
I'd say probably yes, but that will reduce reuse of cached entries.

Kind regards

robert


PS: if you run out of tasks (I know, won't happen) - I just discovered
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-- 
use.inject do |as, often| as.you_can - without end