Register an object method for notifications. Based on the idea of notifications in objective-C.
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README.rdoc
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central_notifications.gemspec

README.rdoc

Overview

Based on the idea of notifications in objective-C.

Register an object method for notifications.

When registered method is called, all objects which have registered will be notified and will be able to know the result of the registered method.

Can act as Rails observers, by registering on setters methods.

You can register both class or instance methods.

Several different objects, with different class can register for same object method.

See tests units for more examples of usage.

Quality Metrics

Continuous Integration

Install

gem install central_notifications

Dependencies

none

Usage

Declaring a notifier

In the model

You can declare a notifier inside the model by including the module CentralNotifications and then declare in you model :

register_for_notification do |registration, notification|
  registration.klass = Order
  registration.method = :payment
  notification.method = :one_order_has_been_payed
end

In this way you don't have to declare the notification klass, it will be automatically set to self.

In an initializer

You can register your notification in an initializer (for exemple, in Rails, in a file under config/initializers).

The analog as previous example will be in this initializer :

CentralNotifications.notify do |registration, notification|
  registration.klass = Order
  registration.method = :payment
  notification.klass = User
  notification.method = :one_order_has_been_payed
end

Example

Suppose you have classes User and Order, and, you have registered for notification on instance method :payment (as previous)

class User
  def one_order_has_been_payed
   puts "Hey! one user know that one order has been paid!"
  end
end

def Order
  def payment(amount)
    @amount = amount
  end
end

user = User.new
order = Order.new
order.payment(100)
# => "Hey! one user know that one order has been paid!"

If you register notification for another class objects :

class Acounting
  include CentralNotification

  def one_order_has_been_payed
    "Hey ! an accounting object know that one order has been payed"
  end

  register_for_notification do |registration, notification|
    registration.klass = Order
    registration.method = :payment
    notification.method = :one_order_has_been_payed
  end
end

then :

user = User.new
accounting = Accounting.new
order = Order.new
order.payment(100)

 # => "Hey! one user know that one order has been paid!"
 # => "Hey ! an accounting object know that one order has been payed"

Retrieve the result of the registered method

You can get in User class the result of Order#payment in the instance variable @registration_result.

def one_order_has_been_payed
  puts "Payment is : " + @registration_result.to_s
end

user = User.new
order = Order.new
order.payment(100)

# => "Payment is : 100"

Retrieve the object which trigger the notification

You can get in User class the result of Order#payment in the instance variable @registration_result.

def one_order_has_been_payed
  puts "payment has been called by this object : " + @notifier_object
end

user = User.new
order = Order.new
order.payment(100)

# => "payment has been called by this object : <Order: ....>"

Acting as Observer

You can use central notifications as observers on attribute values change. For that, just register on setter :

  class Order
    attr_accessor :amount
  end

  class User
    include CentralNotification

    def amount_has_changed
      puts "The amount has changed and is now:" + @registration_result.to_s
    end

    register_for_notification do |registration, notification|
      registration.klass = Order
      registration.method = :amount=
      notification.method = :amount_has_changed
    end
  end

user = User.new
order = Order.new
order.amount = 100
#=> From user : The amount has changed and is now: 100

ChangeLog

  • FIX : Failures with Ruby 1.9 . #instance_methods, #singleton_methods … family methods return symbols. Ruby 1.8.x return strings.

  • NEW : Notified method has access to object which triggered notification