Metaprogramming in Squeak

Apr 8, 2008 at 10:55 AM
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In comp.lang.smalltalk today, I got to answer a simple question about metaprogramming. My classic example is being able to create an anonymous class simply by calling "Behavior New". Here's my code:

   | myClass myInstance |
   myClass := Behavior new. "create anon behavior"
   myClass compile: 'theAnswer ^42'. "add a method for instances"
   myInstance := myClass new. "create an instance"
   Transcript show: myInstance theAnswer; cr. "shows 42"

There might be some more responses in the thread, or maybe you can add some of your own. Enjoy.

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You can even set an object to be its own class, and hence get real prototype-oriented instances on Squeak.

oroboros := Class new.

oroboros superclass: Class. oroboros methodDictionary: MethodDictionery new. oroboros setFormat: Class format. oroboros primitiveChangeClassTo: oroboros basicNew

oroboros class = oroboros --> true

More see here http://smallwiki.unibe.ch/adriankuhn/protalk/

Wow! Thanks a lot for this. A while back I was poking around inside Squeak to try to find out how to dynamically compile code. I already knew about Compiler evaluate:, which I could use to compile a BlockClosure, for example. During my search I kept running into the Behavior class, but I didn't know what it really represented or what it could do. I was also running into methods to compile methods, but I didn't see any examples of how to use them. As descriptive as Smalltalk code is, unfortunately it's not always self-explanatory. Examples help.

Metaprogramming in Squeak

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