aspect4r

Aspect Oriented Programming support for Ruby

Feature

extract common logic from multiple methods into before, after, around advices
before_filter as method filters (work like before_filters in web application)
advices can be customized (e.g. to take an optional method name argument)
work as a supporting piece for more complex AOP tasks

Usage

API documentation: gcao.posterous.com/aspect4r-usage-and-public-api

class A
  include Aspect4r

  around :test do |proxy_method, value|
    a4r_invoke proxy_method, value
  end

  before :test do |value|
    puts "entering test(#{value})"
  end

  before :test, :do_something

  before_filter :test do |value|
    value >= 0
  end

  after :test do |result, value|
    puts "test(#{value}) returned #{result}"
    result
  end

  after :test, :do_something_else

  def test value
    ...
  end

  def do_something value
    ...
  end

  def do_something_else result, value
    ...
  end

end

How does it work?

Execution model: gcao.posterous.com/aspect4r-documentation-advice-execution-model

TODO

See github issues github.com/gcao/aspect4r/issues

Support regular expression on methods to be advised. When such an advice is defined, methods defined before it will not be processed, only new methods are.

Advices are stored in an array. Whenever a method is created, the whole array is checked to find the advices that are applicable to it. Those applicable advices are used to construct the new method. This provides a lot flexibilities but can be a performance burden.

One way to improve performance is to use array to store advices that use regular expression. Advices specific to methods are stored in hash. (Do this only when performance is proved to be a problem in real world scenarios)

Advice name: each advice can take a :name option. If no name is given, the advice method name is used as the advice name. If advice logic is in a block and :name is not set, the advice will not have a name. Multiple advices can have same name. What use can this bring? skip advice for specific methods. debugging purpose. testing purpose.

Inherit advices: add option :inherit to all advices. Advices whose :inherit options are set to true will be copied to child modules/classes. By default :inherit is set to false. This adds a lot complexity and might not be a good idea. This can be achieved by putting advices in ModuleX.included or ClassY.inherited

a4r_remove_advices: will remove advices with given names. If no name is given, all advices are removed.

Note on Patches/Pull Requests