From: Rich Kilmer <rich@...>
Date: 2002-04-02T23:22:12+09:00
Subject: RE: Creating an instance of a class without calling initialize()



> -----Original Message-----
> From: Harry Ohlsen [mailto:harryo@zip.com.au]
> Sent: Monday, April 01, 2002 7:11 PM
> To: ruby-talk ML
> Subject: Re: Creating an instance of a class without calling
initialize()
> 
> "Rich Kilmer" <rich@infoether.com> wrote in message
> 
> > You actually may want to recommend that he use:
> >
> > obj = new
> >
> > FOR EACH ATTRIBUTE
> >   obj.instance_eval "@#{attributeName}=#{attributeValue}"
> > END
> >
> > That way it works for attributes that do not have writer methods but
> > only reader methods (ie. Foo.x but not Foo.x=)
> 
> Unfortunately, that won't work very well if the attribute
> value is an instance of an arbitrarily complex class, since
> what it's effectively trying to do is de-serialise/re-serialise
> atrributeValue as text :-).
> 

My bad here...I should have written:

obj = new

FOR EACH ATTRIBUTE
   eval "obj.instance_eval {@#{attributeName}=attributeValue}"
END

That way what you are doing is a local eval (which has attributeValue in
its local scope) and passing a block to instance_eval (which will then
have @'attributeName' in its local scope) so string stuff is avoided.

Assuming the attributeName = x, this would be the same as doing

obj.instance_eval {@x=attributeValue}

Cool, huh?

-Rich