Subject: Re: testing object inheritance
From: Craig Chambers (chambers@cs.washington.edu)
Date: Sat Nov 04 2000 - 13:23:15 PST
This is an intentional design feature. It's consider Morally Wrong to be
testing the run-time inheritance of an object. You've violated its
abstraction. If there's something you'd like to do with an object, then you
define the appropriate methods on it. This can often take the form of a bunch
of is_foo, if_foo(true & false continuations), but then the user has introduced
an abstraction "foo" that is conceptually unrelated to the underlying
inheritance of the object. Any object can claim that it is a "foo", independent
of how it's implemented. Cecil forces you to write these instanceof methods
yourself, in order to save you from the Sin of violated an object's integrity.
Or at least that's the philosophy. Syntactic sugar might make this philosophy
easier to swallow.
-- Craig
Keunwoo Lee wrote:
>
> There is no equivalent of dynamic_cast in Cecil, as I discovered to my
> dismay when writing my exceptions lib. Add a temporary method
> isa_foo(@foo):bool for each class if you want to do class testing, or a
> print_class(@foo) if you want to know about the class.
>
> ~k
>
> On Wed, 1 Nov 2000, Sorin Lerner wrote:
>
> > Is there a way in Cecil to determine if an object inherits from another
> > object O, even if O is abstrat. I have a variable "node', and I tried
> > node.inherits_from(IntLiteralNode). This however caused a run-time error
> > because IntLiteralNode is an abstract object. Is there a way around
> > this?
> >
> > Sorin
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