Aspector

Aspector = ASPECT Oriented Ruby programming

Deprecated

Aspector is deprecated.

We recommend Ruby native Module#prepend functionality to build up aspects.

About

Aspector allows to use aspect oriented programming with Ruby.

Aspector allows adding additional behavior to existing code (an advice) without modifying the code itself, instead separately specifying which code is modified via a "pointcut" specification.

Highlights

Encapsulate logic as aspects and apply to multiple targets easily
Support before/before_filter/after/around advices
Work anywhere - inside/outside the target class, before/after methods are created
Use regexp matching to apply advices to multiple methods
Small codebase, intuitive API
Conditional aspects disabling/enabling
Standarized logging API
Aspects are applicable to both classes/modules and instances
Object extensions for easier usage

Example usages

Aspector should be used whenever you have a cross-cutting concerns, especially when they don't perform any business logic. For example use can use it to provide things like:

Logging
Monitoring
Performance benchmarking
Any type of transactions wrapping
Events producing for systems like Apache Kafka
Etc...

Installation

gem install aspector

or put it inside of your Gemfile:

gem 'aspector'

Examples

To see how to use Aspector, please review examples that are in examples directory.

If you need more detailed examples, please review files in spec/functionals and spec/units/advices.

Here's a simple example how Aspector can be used:

class ExampleClass
  def test
    puts 'test'
  end
end

aspect = Aspector do
  target do
    def do_this
      puts 'do_this'
    end
  end

  before :test, :do_this

  before :test do
    puts 'do_that'
  end
end

aspect.apply(ExampleClass)
element = ExampleClass.new
element.test
aspect.disable!
element.test

# Expected output
# do_this
# do_that
# test
# test

Configuration options

Aspector is really easy to use. After installation it doesn't require any additional configuration. You can however set two environments variables that are related to logging:

ENV variable name	Description
ASPECTOR_LOGGER	Any logger class you want to use (if you don't want to use Aspector standard logger)
ASPECTOR_LOG_LEVEL	DEBUG < INFO < WARN < ERROR < FATAL < UNKNOWN

Aspector::Logger inherits from a standard Ruby logger. Log levels and the API are pretty standard. You can however use yor own:

ASPECTOR_LOGGER='MyApp::Logger' ASPECTOR_LOG_LEVEL='any log level' ruby aspected_stuff.rb

Default and apply options

Here are options that you can use when creating or applying a single aspect:

Option name	Type	Description
except	Symbol, String, Regexp or Array of those	Will apply aspect to all the methods except those listed
name	String	Advice name (really useful only for debugging)
methods	Array of Symbol, String, Regexp	Method names (or regexp for matching) to which we should apply given aspect
method	Symbol, String, Regexp or Array of those	Acts as methods but accepts a single name of method (or a single regexp)
existing_methods_only	Boolean (true/false) - default: false	Will apply aspect only to already defined methods
new_methods_only	Boolean (true/false) - default: false	Will apply aspect only to methods that were defined after aspect was applied
private_methods	Boolean (true/false) - default: false	Should the aspect be applied to private methods as well (public only by default)
class_methods	Boolean (true/false) - default: false	Should the aspect for instance methods of class methods of a given element
method_arg	Boolean (true/false) - default: false	Do we want to have access to base method arguments in the aspect method/block
interception_arg	Boolean (true/false) - default: false	Do we want to have access to the interception instance in the aspect method/block

Contributing to aspector

Check out the latest master to make sure the feature hasn't been implemented or the bug hasn't been fixed yet
Check out the issue tracker to make sure someone already hasn't requested it and/or contributed it
Fork the project
Start a feature/bugfix branch
Commit and push until you are happy with your contribution
Make sure to add specs for it. This is important so I don't break it in a future version unintentionally.
If it is a new functionality or feature please provide examples
Please benchmark any functionality that might have a performance impact
Please try not to mess with the Rakefile, version, or history. If you want to have your own version, or is otherwise necessary, that is fine, but please isolate to its own commit so I can cherry-pick around it.

aspector