[Newbies] Ruby macros
bert at impara.de
Sun Jul 2 11:20:44 UTC 2006
Am 02.07.2006 um 06:33 schrieb itsme213:
> I miss my Ruby macros (1st day in Squeak and I love it ... dislike
> the camelCase tho').
To add a variable to a class, use
someClass addInstVarName: 'myInstVar'.
To add an accessor with initialization code, compile one:
someClass compile: 'myInstVar ^myInstVar ifNil: [myInstVar :=
Similarly, use #removeInstVarName: and #removeSelector: to remove
what you added.
To automate the process, you could implement #noteCompilationOf:meta:
to add/remove stuff automatically when some "spec" method was changed.
HOWEVER, such "magic" behavior is not considered good practice in
Smalltalk. We do use code generation for repetitive tasks, but that
is usually triggered not automagically, but invoked manually - we put
the actual call in a comment that you can just double-click and
execute. An example for this is the various "#fields" methods for
ExternalStructure subclasses which include a "self defineFields"
comment that should be executed when you changed the field definitions.
The reason for this non-magic is mostly because you're dealing with
an evolving, live system that is not bootstrapped every time you run
your app like in Ruby. After you let the system define the methods,
you're free to change them in a browser to suit your needs. In
Smalltalk, you're actually modifying the class, not a textual blue-
print that is executed later. That's a huge difference, it's hard to
grasp when you come from a different environment, admittedly, but you
need to get your head around it to become a proficient Smalltalker.
Once you got enlightened, you'll wonder how you could ever have
longed for editing a Smalltalk class in a text file ;-)
- Bert -
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