https://github.com/steveklabnik/active_record-observers

https://github.com/steveklabnik/active_record-observers

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• Host: GitHub
• URL: https://github.com/steveklabnik/active_record-observers
• Owner: steveklabnik
• License: mit
• Created: 2012-08-10T04:19:51.000Z (over 12 years ago)
• Default Branch: master
• Last Pushed: 2012-11-28T23:02:11.000Z (about 12 years ago)
• Last Synced: 2024-12-16T23:03:31.239Z (7 days ago)
• Language: Ruby
• Size: 188 KB
• Stars: 2
• Watchers: 2
• Forks: 1
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# Rails::Observers

Rails Observers (removed from core in Rails 4.0)

## Installation

Add this line to your application's Gemfile:

    gem 'rails-observers'

And then execute:

    $ bundle

Or install it yourself as:

    $ gem install rails-observers

## Usage

This gem contains two observers:

* Active Record Observer

* Action Controller Sweeper

### Active Record Observer

Observer classes respond to life cycle callbacks to implement trigger-like

behavior outside the original class. This is a great way to reduce the

clutter that normally comes when the model class is burdened with

functionality that doesn't pertain to the core responsibility of the

class. Example:

```ruby

class CommentObserver < ActiveRecord::Observer

  def after_save(comment)

    Notifications.comment("[email protected]", "New comment was posted", comment).deliver

  end

end

```

This Observer sends an email when a Comment#save is finished.

```ruby

class ContactObserver < ActiveRecord::Observer

  def after_create(contact)

    contact.logger.info('New contact added!')

  end

  def after_destroy(contact)

    contact.logger.warn("Contact with an id of #{contact.id} was destroyed!")

  end

end

```

This Observer uses logger to log when specific callbacks are triggered.

### Action Controller Sweeper

Sweepers are the terminators of the caching world and responsible for expiring caches when model objects change.

They do this by being half-observers, half-filters and implementing callbacks for both roles. A Sweeper example:

```ruby

class ListSweeper < ActionController::Caching::Sweeper

  observe List, Item

  def after_save(record)

    list = record.is_a?(List) ? record : record.list

    expire_page(:controller => "lists", :action => %w( show public feed ), :id => list.id)

    expire_action(:controller => "lists", :action => "all")

    list.shares.each { |share| expire_page(:controller => "lists", :action => "show", :id => share.url_key) }

  end

end

```

The sweeper is assigned in the controllers that wish to have its job performed using the `cache_sweeper` class method:

```ruby

class ListsController < ApplicationController

  caches_action :index, :show, :public, :feed

  cache_sweeper :list_sweeper, :only => [ :edit, :destroy, :share ]

end

```

In the example above, four actions are cached and three actions are responsible for expiring those caches.

You can also name an explicit class in the declaration of a sweeper, which is needed if the sweeper is in a module:

```ruby

class ListsController < ApplicationController

  caches_action :index, :show, :public, :feed

  cache_sweeper OpenBar::Sweeper, :only => [ :edit, :destroy, :share ]

end

```

## Contributing

1. Fork it

2. Create your feature branch (`git checkout -b my-new-feature`)

3. Commit your changes (`git commit -am 'Added some feature'`)

4. Push to the branch (`git push origin my-new-feature`)

5. Create new Pull Request