Injection is a simple dependency injection plugin for Rails 3. It allows you to inject objects into your controllers and observers which have been described in a yaml file (config/objects.yml).

• github.com/atomicobject/injection

(for the Rails 2 plugin install from the rails_2_plugin tag of this repository)

• Declarative dependency injection that automatically instantiates ivars via the objects.yml file

To specify objects to be injected from the DIY context into your controller or observer
use the inject class method:

  inject :one_component, :another

This example defines a context with two objects, _foo_ and _bar_, which 
are injected into every instance of the WidgetController or WidgetObserver.  The objects 
are available as instance variables within the controller and observer.

config/objects.yml:
  ---
  foo:
  bar:

lib/foo.rb:
  class Foo
    ...
  end

lib/bar.rb:
  class Bar
    ...
  end

app/controllers/widget_controller.rb:
  class WidgetController < ApplicationController
    inject :foo, :bar

    def index
      render :text => "{@foo.inspect} {@bar.inspect}"
    end
  end

app/models/widget_observer.rb:
  class WidgetObserver < ActiveRecord::Observer
    inject :foo, :bar

    before :save do |widget|
     @foo.bar(widget)
     @bar.foo(widget)
    end
  end

Observations on an Active Record object can be specified in a declarative way using
the before and after class methods. The methods are invoked with a
symbol which specifies what kind of event the observer is interested in, and a block 
that defines what actions it will perform.

  class WidgetObserver < ActiveRecord::Observer
    before :update do |record|
      ...
    end

    after :create do |record|
      ...
    end

    after :validation do |record|
      ...
    end

    before :validation do |record|
      ...
    end
  end

• constructor

• diy

• gem install injection

(The MIT License)

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