From: Aristarkh A Zagorodnikov <xm@...>
Date: 2001-11-11T16:56:28+09:00
Subject: [ruby-talk:24863] Re: Help needed on subclassing


> -----Original Message-----
> From: Bob Gustafson [mailto:bobgus@mcs.com]
> Sent: Sunday, November 11, 2001 9:44 AM
> To: ruby-talk ML
> Subject: [ruby-talk:24860] Re: Help needed on subclassing
>
>
> >Its late here in Sweden (actually early, but anyway... ;-)) and I cant
> >find an elegant way to from class M subclass class T so that in
> >the subclass some (but not all) of the arguments for T.new are specified.
> >
> >Example:
> > T is class with T.new(a,b,c)
> > M.[] needs to return a subclass of T (lets call it S) so that calls
> >       S.new(c) are translated to T.new(am,bm,c).
> >
> >Ok, you can use evals but I'd call that cheating.
> >
> >Please help me; my brain and screen are hazy! ;-)
> >
> >/Robert
>
> Why not do
>
> def T.new(a=defaulta,b=defaultb,c=defaultc)
>
> Except that you probably need to put the c first
>
> def T.new(c=defaultc, a=defaulta,b=defaultb)
Using default parameters isn't any good I believe.
If I understood you corrctly you'll need something like this:

class T
	def initialize(a, b, c)
		............
	end
end

class S < T
	def self.new(c)
		super -12, "nothing more than a test string", c
	end
end

class M
	def [](arg)
		S.new 47
	end
end

_____________________________________________________________
Zagorodnikov Aristarkh | Lead Programmer | xm@bolotov-team.ru
bolotov.ru creative group
http://www.bolotov.ru/