This is a DataMapper plugin that provides observers for DataMapper resource
classes. It's compatible with DataMapper 0.9.1

== Setup
DataMapper observer capabilities are automatically available when you
'require dm-observers' into your application.

== Basic Usage

  require 'dm-observers'

  DataMapper.setup(:default, 'sqlite3::memory:')

  class MyModel
    include DataMapper::Resource
    include DataMapper::Observers::Observable
    property :id, Integer, :key => true
  end

  class MyObserver < DataMapper::Observers::Observer
    def before_save(object)
      puts "Before save..."
      # ...
    end
  
    def after_save(object)
      puts "After save..."
      # ...
    end
  
    # ...
  end

  MyModel.add_observer(MyObserver.instance)

  MyModel.new.save

---- output ----
Before save...
After save...
---- output ----


The following are the hooks that are automatically called on the observers
before or after each model CRUD operation, if they are defined:

before_save, after_save, before_create, after_create, before_update, after_update,
before_destroy, after_destroy


== Observers for DataMapper Resources

The observers defined for DataMapper Resources can be automatically added to the model,
if the observer class name is prefixed with the name of the model to observe, and suffixed
with 'Observer'. Example:

  class MyModel
    # ...
  end

  class MyModelObserver
    # ...
  end

  MyModelObserver.instance # The observer is automatically added to the MyModel class.


You can include all the observers instanciations at some bootstrap block of your project.


== Custom messages to the observer

Additionally to the default hooks called on the observers, you can send a custom message
to them using the notify_observers method:

  class MyModel
    include DataMapper::Resource
    include DataMapper::Observers::Observable
    property :id, Integer, :key => true
  
    def do_something
      # ...
      MyModel.notify_observers(:purge_old_data, self)
    end
  end

  class MyModelObserver < DataMapper::Observers::Observer
    def purge_old_data(object)
      puts "Purge Old Data..."
      # ...
    end
  end

  MyModelObserver.instance
  MyModel.new.do_something