Introduction to ActiveRecord

1. ACTIVERECORD
(AKA Why Rails doesn’t scale.)

2. CREATING NEW OBJECTS
• Model#new
• Model#create
• model.association.build
• :touch => (rails 2.3)
http://ryandaigle.com/articles/2009/4/20/what-s-new-in-edge-rails-touching

3. CLASS METHODS
• find
• find_by*
• find :include => :other_model (n+1)
• find :join => :other_model

4. ASSOCIATIONS
• has_one, has_many
• has_and_belongs_to_many
• belongs_to
• :through =>

5. ASSOCIATION METHODS
• scoping methods on associations

6. SCOPING
• with_scope
around_filter, scopes all finds to parent model
• named_scopes
• dynamic_scope (2.3)
http://ryandaigle.com/articles/2008/12/29/what-s-new-in-edge-rails-dynamic-scope-methods

7. VALIDATIONS
• built in validations
• validate :some_method

8. CALLBACKS AND OBSERVERS
• Transactional Semantics for free

9. LAW OF DEMETER
• Structure vs Ecapsulation

10. PLUGINS
• acts_as_list
• acts_as_nested_set
• acts_as_tree