On Thursday 26 June 2008 13:07:04 Nick Smith wrote:
I'm a newbie to programming and I'm really enjoying learning Squeak, Seaside. One of the biggest delights for me is discovering just how expressive and powerful Smalltalk is when you can so easily add your own methods to the base classes. By using good intention-revealing selector names, I can write code that is almost self-explanatory.... like prose but not in the language of Smalltalk, in the language of the application/problem domain itself. This is brilliant. Every program you write is it's own DSL.
So here's the thing I don't yet understand. If I embrace this way of programming and extend bases classes by adding my own methods, what happens to those methods when I upgrade my image to a newer version of Squeak? Is it that I need to subclass existing base classes before extending them (to better separate my code from the original) or perhaps I need to learn to use Traits; or is there something about Monticello that allows me to migrate my custom methods to newer images? Or maybe perhaps there's something I've missed completely.
You can use changes set or packages (with Monticello). It seems to me that Monticello is what you are looking for.
By convention, a package XXX owns all classes that are defined within a system category which name start with 'XXX-' and owns all methods that are defined within a method category which name start with '*xxx-'.
Let's try following example:
- Create a class A with 'XXX-base' as its system category and a class B with 'XXX-util' as its system category. - Open Monticello, click on '+package' button and type 'XXX'. - Then select and browse XXX package ('Browse' button). A package browser is opened on XXX package (showing your two system categories 'XXX-base' and 'XXX-util').
- Now Browse class String with a standard browser, create a method category named '*xxx-for-my-test' (don't forget the $* at the beginning of the category name). - Create a method within '*xxx-for-my-test', as an example: forMyTest ^ self
- Then, open Monticello and browse your package again. On left package browser list, select '*Extensions' item. you should see your String>>forMyTest method in. This means that String>>forMyTest owns to XXX package. Yes! you got it! (this was the main subject of your question I guess).
Now the question is, how to save a package and import it from another squeak image. - For file out, select your package from Monticello then select a repository (at least the local one is present) and click on 'Save' button. - Then open a file list and browse 'package-cache' sub directory. you should see a file named 'XXX.<your-initials>.1.mcz'. This is your XXX package.
- Then open another squeak image (a fresh one, without XXX package). - Open a file list, browse 'package-cache' sub directory, select 'XXX.<your-initials>.1.mcz' and click on 'Load' button.
After that, your package is loaded, comprising extension methods (your String>>forMyTest).
Cheers alain
Thanks.