Re: Subclass
Re: Subclass
- Subject: Re: Subclass
- From: Chris Hanson <email@hidden>
- Date: Sun, 15 Jun 2003 15:55:36 -0500
On Sunday, June 15, 2003, at 02:32 PM, Dustin Voss wrote:
On Saturday, June 14, 2003, at 05:01 PM, Chris Hanson wrote:
These are nonsensical in a true object-oriented language; since you
can send any message to any object at any time, there is and can be
no enforcement of protection.
Why ever would you think that a "true" OO language should not -- and
*can* not -- have protected/private methods? Smalltalk is not the
end-all and be-all, you know.
Smalltalk may not be the be-all and end-all of programming languages,
but in quite literal terms it is the *definition* of object-oriented.
If you want enforcement of protection, it is up to the receiver of a
message to enforce it at run time. Some Smalltalk implementations
actually have a "sender" metavariable like the "self" and "super"
metavariables that refers to the sender of a message in a method and
can be used for just this purpose.
I don't think this would be an unreasonable extension to the
Objective-C language, though it would (a) break a ton of existing code
since the signature to objc_sendMsg() and every individual method would
have to change to support it -- framework versioning could help here;
(b) slow things down slightly because it would require an additional
argument to be passed to every single method; and (c) be tricky to work
out exactly what should happen in the case of forwarding (especially in
the context of DO).
Now, maybe you're not really asking for true enforcement of protection.
Maybe you're just asking for the ability to declare methods as being
@protected or @private and then have the compiler issue a warning (if
possible) when you try to send the corresponding message in an
inappropriate context. That would be acceptable since it wouldn't
represent a fundamental corruption of the language in the way that true
protection enforcement would. It would just be a compile-time hint to
developers just like static typing, not a hard restriction like it is
in other languages like C++ and Java, and therefore wouldn't get in the
way like it does in those languages.
Don't get me wrong. I think there are plenty of things that could be
improved about Objective-C -- Smalltalk sets the bar quite high, and
while Objective-C gets a lot closer than C++ or Java, it's still got a
ways to go. There are even some things that could be improved about
Smalltalk. The way to improve Objective-C is *not* to try to turn it
into C++ or Java, but rather to try to bring it even closer to
Smalltalk.
(Off the top of my head: Support for unloading & reloading classes,
much cleaner category semantics, true class variables, blocks, true
metaclasses, language-level exceptions rather than setjmp/macro
exception handling, garbage collection, support for UTF-8 source
files...)
-- Chris
--
Chris Hanson, bDistributed.com, Inc. | Email: email@hidden
Custom Application Development | Phone: +1-847-372-3955
http://bdistributed.com/ | Fax: +1-847-589-3738
http://bdistributed.com/Articles/ | Personal Email: email@hidden
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| | >Re: Subclass (From: Dustin Voss <email@hidden>) |