AspectR - Simple aspect-oriented programming in Ruby
====================================================
Version:          0.3.5
Release date:     2002-01-29
Home page:        http://aspectr.sf.net/
Tarball:          http://prdownloads.sf.net/aspectr/aspectr-0-3-5.tar.gz
Authors:          Avi Bryant and Robert Feldt
Email:            avi@beta4.com, feldt@ce.chalmers.se

What is it?
-----------
Aspect-oriented programming concepts to Ruby. Essentially 
it allows you to wrap code around existing methods in your classes. 
This can be a good thing (and even affect how you design your code) since 
it separates different concerns into different parts of the code. 
It is somewhat similar to AspectJ, www.aspectj.org.

Main features of AspectR (in AspectJ lingo): 
* Join points: 
    - object receives method/constructor call, and 
    - field accessed (if access is via getter/setter meth) 
* Advices: before (pre), after returning and after throwing (post) 
* Aspects: classes inheriting Aspect. 
    - supports "abstract" Aspects and overriding between advices. 
* Wildcards (really regexps) can be used in pointcut designators, ie. to 
  specify classes and methods to wrap advice's to. 
* Pointcut parameters. Advices can access: 
    - object and method receiving call, 
    - arguments to call, 
    - return values, and 
    - exceptions raised. 

Installation?
-------------
1. unpack tarball (if you haven't already)
2. install: ruby install.rb
3. If you've got RubyUnit you can also run tests: ruby tests/runtests.rb

Example of use?
---------------
See tests, try out examples/logger.rb or check out the aspects in the aspects
subdir.

Documentation?
--------------
AspectR lets a module wrap any number of methods in other classes 
(or objects) with the "advice" methods (in the lingo of Aspect/J) 
of the module.

Usage:
 require 'aspectr'
 include AspectR
 class MyAspect < Aspect
	def someAdviceMethod(method, object, exitstatus, *args)
	     ...
      end
	... some other advice methods ...
 end
 ma = MyAspect.new
 ma.wrap(someClassorObject, :preAdvice, :postAdvice, ... methods to wrap...)
 or
 ma.wrap(someClassorObject, :preAdvice, :postAdvice, /patternToWrap/)
 or
 AspectR.wrap_classes(ma, :preAdvice, :postAdvice,
                      [Class1, Class2], ...methods to wrap...)

Advice methods are passed a variable number of parameters:
the first is the name of the method currently being wrapped
the second is the object receiving the method call
the third is the exit/return status:
	Array with return value(s) if the method exited normally
	true if the method exited with an exception
	nil if the method hasn't yet exited (for preAdvice)
the rest are the arguments that were passed to the wrapped method.

I'm confused by the different version of this? What is/was 'advice.rb'?
-----------------------------------------------------------------------
AspectR was originally called advice.rb and written by Avi Bryant.
Later Robert Feldt changed/tweaked/extended it. Avi then refactored very
nicely, Robert tweaked a bit more and on it goes... ;-) For details see 
CHANGELOG.

License and legal issues?
-------------------------
All files in this package are 
Copyright (c) 2001 Avi Bryant (avi@beta4.com) and Robert Feldt (feldt@ce.chalmers.se) 

and they are distributed under GPL. See COPYING.TXT.

Plans for the future?
---------------------
See TODO. This is an alpha release so there might be (some) changes 
to the interface.

How does AspectR differ from AspectJ?
-------------------------------------
AspectJ features that AspectR is missing:
  * Join points: method/constructor called, method/constructor executes (?),
      exception handler executes
  * Most of the pointcut designator primitives
  * Composition of pointcut designators (well you can of course specify 
      several method calls in different classes and objects)
  * 'around' advices (should be pretty easy to add if there's a benefit)
  * precedence/specificity among advices/aspects
  * reflection by sending joinpoint object to advices with context of join
      point etc (easily added but why?)
  * control-flow based crosscutting (might be possible if we locally attach
      a trace func but are they needed?)

Do you have comments or questions?
----------------------------------
We'd appreciate if you drop us a note if you're using 
AspectR. If there are some known users we'll be more motivated to 
pack up additions / new versions and post them to RAA.

Happy coding!

Avi and Robert