On Fri, Oct 12, 2012 at 9:21 AM, Chris Cunnington
<smalltalktelevision at gmail.com> wrote:

> And so I'm guessing that this idea of splitting a protocol from its class
> has bled into Squeak from Objective-C in the form of Traits. Casimiro must
> have a reason for using them that he likes. But they do seem like a
> workaround as a result of a shallow hierarchy. I think I'd rather create my
> own abstract superclass to define an interface.

You might find this interesting:

http://www.jot.fm/issues/issue_2002_05/article1/

It's a paper about SmallInterfaces, which created first-class
interfaces (in Java parlance) for Smalltalk. There was a Squeak port
that ran in Squeak 3.2 IIRC.

I find it much more fruitful to think about protocols rather than
classes when designing or analyzing OO systems. This fits in nicely
with what you said about composition being better than inheritance.
But there are a few issues with a protocol-centric view in Smalltalk:

One is that we don't really need formal protocols the way Java or
Objective-C do, because of the flexibility of Smalltalk. Objective-C
uses protocols to allow classes to be extended even when you don't
have the source code to the object that you're extending. Java uses
interfaces to allow polymorphism between classes that aren't related
by inheritance. In both cases, formalized protocols work around a
problem caused by the mechanics of the language or it's tools. In
Smalltalk, doing everything in-image, we don't have those problems.

Given that protocol-oriented programming is so good, it would be nice
to have better support for that mode of thinking. I bet, for example,
that there's a latent "Map" protocol in the image, which is a subset
of the methods that Dictionary implements. It's #at: and #at:put: plus
a few other supporting methods, but *not* the whole protocol
implemented by Dictionary and certainly not all the stuff it inherits
from Collection. I'd love to see a tool that would let us discover
these latent protocols, name them, and then view and manipulate the
system based on them.

Colin