HappyGoLucky: ActiveRecord Code Hacking

Class ActiveRecord::Schema < Migration

Allows programmers to programmatically define a schema in a portable DSL. This means you can define tables, indexes, etc. without using SQL directly, so your applications can more easily support multiple databases.

Class ActiveRecord::Observer < Object

In: lib/active_record/observer.rb

Observer classes respond to lifecycle 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:

  class CommentObserver < ActiveRecord::Observer
    def after_save(comment)
      Notifications.deliver_comment("admin@do.com", "New comment was posted", comment)
    end
  end

Class ActiveRecord::ConnectionAdapters::AbstractAdapter < Object

In: lib/active_record/connection_adapters/abstract_adapter.rb

All the concrete database adapters follow the interface laid down in this class. You can use this interface directly by borrowing the database connection from the Base with Base.connection.