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diff --git a/activerecord/README b/activerecord/README deleted file mode 100644 index 0446180207..0000000000 --- a/activerecord/README +++ /dev/null @@ -1,336 +0,0 @@ -= Active Record -- Object-relation mapping put on rails - -Active Record connects business objects and database tables to create a persistable -domain model where logic and data are presented in one wrapping. It's an implementation -of the object-relational mapping (ORM) pattern[http://www.martinfowler.com/eaaCatalog/activeRecord.html] -by the same name as described by Martin Fowler: - - "An object that wraps a row in a database table or view, encapsulates - the database access, and adds domain logic on that data." - -Active Record's main contribution to the pattern is to relieve the original of two stunting problems: -lack of associations and inheritance. By adding a simple domain language-like set of macros to describe -the former and integrating the Single Table Inheritance pattern for the latter, Active Record narrows the -gap of functionality between the data mapper and active record approach. - -A short rundown of the major features: - -* Automated mapping between classes and tables, attributes and columns. - - class Product < ActiveRecord::Base; end - - ...is automatically mapped to the table named "products", such as: - - CREATE TABLE products ( - id int(11) NOT NULL auto_increment, - name varchar(255), - PRIMARY KEY (id) - ); - - ...which again gives Product#name and Product#name=(new_name) - - {Learn more}[link:classes/ActiveRecord/Base.html] - - -* Associations between objects controlled by simple meta-programming macros. - - class Firm < ActiveRecord::Base - has_many :clients - has_one :account - belongs_to :conglomorate - end - - {Learn more}[link:classes/ActiveRecord/Associations/ClassMethods.html] - - -* Aggregations of value objects controlled by simple meta-programming macros. - - class Account < ActiveRecord::Base - composed_of :balance, :class_name => "Money", - :mapping => %w(balance amount) - composed_of :address, - :mapping => [%w(address_street street), %w(address_city city)] - end - - {Learn more}[link:classes/ActiveRecord/Aggregations/ClassMethods.html] - - -* Validation rules that can differ for new or existing objects. - - class Account < ActiveRecord::Base - validates_presence_of :subdomain, :name, :email_address, :password - validates_uniqueness_of :subdomain - validates_acceptance_of :terms_of_service, :on => :create - validates_confirmation_of :password, :email_address, :on => :create - end - - {Learn more}[link:classes/ActiveRecord/Validations.html] - -* Callbacks as methods or queues on the entire lifecycle (instantiation, saving, destroying, validating, etc). - - class Person < ActiveRecord::Base - def before_destroy # is called just before Person#destroy - CreditCard.find(credit_card_id).destroy - end - end - - class Account < ActiveRecord::Base - after_find :eager_load, 'self.class.announce(#{id})' - end - - {Learn more}[link:classes/ActiveRecord/Callbacks.html] - - -* Observers for the entire lifecycle - - class CommentObserver < ActiveRecord::Observer - def after_create(comment) # is called just after Comment#save - Notifications.deliver_new_comment("david@loudthinking.com", comment) - end - end - - {Learn more}[link:classes/ActiveRecord/Observer.html] - - -* Inheritance hierarchies - - class Company < ActiveRecord::Base; end - class Firm < Company; end - class Client < Company; end - class PriorityClient < Client; end - - {Learn more}[link:classes/ActiveRecord/Base.html] - - -* Transactions - - # Database transaction - Account.transaction do - david.withdrawal(100) - mary.deposit(100) - end - - {Learn more}[link:classes/ActiveRecord/Transactions/ClassMethods.html] - - -* Reflections on columns, associations, and aggregations - - reflection = Firm.reflect_on_association(:clients) - reflection.klass # => Client (class) - Firm.columns # Returns an array of column descriptors for the firms table - - {Learn more}[link:classes/ActiveRecord/Reflection/ClassMethods.html] - - -* Direct manipulation (instead of service invocation) - - So instead of (Hibernate[http://www.hibernate.org/] example): - - long pkId = 1234; - DomesticCat pk = (DomesticCat) sess.load( Cat.class, new Long(pkId) ); - // something interesting involving a cat... - sess.save(cat); - sess.flush(); // force the SQL INSERT - - Active Record lets you: - - pkId = 1234 - cat = Cat.find(pkId) - # something even more interesting involving the same cat... - cat.save - - {Learn more}[link:classes/ActiveRecord/Base.html] - - -* Database abstraction through simple adapters (~100 lines) with a shared connector - - ActiveRecord::Base.establish_connection(:adapter => "sqlite", :database => "dbfile") - - ActiveRecord::Base.establish_connection( - :adapter => "mysql", - :host => "localhost", - :username => "me", - :password => "secret", - :database => "activerecord" - ) - - {Learn more}[link:classes/ActiveRecord/Base.html#M000081] and read about the built-in support for - MySQL[link:classes/ActiveRecord/ConnectionAdapters/MysqlAdapter.html], PostgreSQL[link:classes/ActiveRecord/ConnectionAdapters/PostgreSQLAdapter.html], SQLite[link:classes/ActiveRecord/ConnectionAdapters/SQLiteAdapter.html], Oracle[link:classes/ActiveRecord/ConnectionAdapters/OracleAdapter.html], SQLServer[link:classes/ActiveRecord/ConnectionAdapters/SQLServerAdapter.html], and DB2[link:classes/ActiveRecord/ConnectionAdapters/DB2Adapter.html]. - - -* Logging support for Log4r[http://log4r.sourceforge.net] and Logger[http://www.ruby-doc.org/stdlib/libdoc/logger/rdoc] - - ActiveRecord::Base.logger = Logger.new(STDOUT) - ActiveRecord::Base.logger = Log4r::Logger.new("Application Log") - - -* Database agnostic schema management with Migrations - - class AddSystemSettings < ActiveRecord::Migration - def self.up - create_table :system_settings do |t| - t.string :name - t.string :label - t.text :value - t.string :type - t.integer :position - end - - SystemSetting.create :name => "notice", :label => "Use notice?", :value => 1 - end - - def self.down - drop_table :system_settings - end - end - - {Learn more}[link:classes/ActiveRecord/Migration.html] - -== Simple example (1/2): Defining tables and classes (using MySQL) - -Data definitions are specified only in the database. Active Record queries the database for -the column names (that then serves to determine which attributes are valid) on regular -object instantiation through the new constructor and relies on the column names in the rows -with the finders. - - # CREATE TABLE companies ( - # id int(11) unsigned NOT NULL auto_increment, - # client_of int(11), - # name varchar(255), - # type varchar(100), - # PRIMARY KEY (id) - # ) - -Active Record automatically links the "Company" object to the "companies" table - - class Company < ActiveRecord::Base - has_many :people, :class_name => "Person" - end - - class Firm < Company - has_many :clients - - def people_with_all_clients - clients.inject([]) { |people, client| people + client.people } - end - end - -The foreign_key is only necessary because we didn't use "firm_id" in the data definition - - class Client < Company - belongs_to :firm, :foreign_key => "client_of" - end - - # CREATE TABLE people ( - # id int(11) unsigned NOT NULL auto_increment, - # name text, - # company_id text, - # PRIMARY KEY (id) - # ) - -Active Record will also automatically link the "Person" object to the "people" table - - class Person < ActiveRecord::Base - belongs_to :company - end - -== Simple example (2/2): Using the domain - -Picking a database connection for all the Active Records - - ActiveRecord::Base.establish_connection( - :adapter => "mysql", - :host => "localhost", - :username => "me", - :password => "secret", - :database => "activerecord" - ) - -Create some fixtures - - firm = Firm.new("name" => "Next Angle") - # SQL: INSERT INTO companies (name, type) VALUES("Next Angle", "Firm") - firm.save - - client = Client.new("name" => "37signals", "client_of" => firm.id) - # SQL: INSERT INTO companies (name, client_of, type) VALUES("37signals", 1, "Firm") - client.save - -Lots of different finders - - # SQL: SELECT * FROM companies WHERE id = 1 - next_angle = Company.find(1) - - # SQL: SELECT * FROM companies WHERE id = 1 AND type = 'Firm' - next_angle = Firm.find(1) - - # SQL: SELECT * FROM companies WHERE id = 1 AND name = 'Next Angle' - next_angle = Company.find(:first, :conditions => "name = 'Next Angle'") - - next_angle = Firm.find_by_sql("SELECT * FROM companies WHERE id = 1").first - -The supertype, Company, will return subtype instances - - Firm === next_angle - -All the dynamic methods added by the has_many macro - - next_angle.clients.empty? # true - next_angle.clients.size # total number of clients - all_clients = next_angle.clients - -Constrained finds makes access security easier when ID comes from a web-app - - # SQL: SELECT * FROM companies WHERE client_of = 1 AND type = 'Client' AND id = 2 - thirty_seven_signals = next_angle.clients.find(2) - -Bi-directional associations thanks to the "belongs_to" macro - - thirty_seven_signals.firm.nil? # true - - -== Philosophy - -Active Record attempts to provide a coherent wrapper as a solution for the inconvenience that is -object-relational mapping. The prime directive for this mapping has been to minimize -the amount of code needed to build a real-world domain model. This is made possible -by relying on a number of conventions that make it easy for Active Record to infer -complex relations and structures from a minimal amount of explicit direction. - -Convention over Configuration: -* No XML-files! -* Lots of reflection and run-time extension -* Magic is not inherently a bad word - -Admit the Database: -* Lets you drop down to SQL for odd cases and performance -* Doesn't attempt to duplicate or replace data definitions - - -== Download - -The latest version of Active Record can be installed with Rubygems: - -* gem install activerecord - -Documentation can be found at - -* http://api.rubyonrails.org - - -== License - -Active Record is released under the MIT license. - - -== Support - -The Active Record homepage is http://www.rubyonrails.com. You can find the Active Record -RubyForge page at http://rubyforge.org/projects/activerecord. And as Jim from Rake says: - - Feel free to submit commits or feature requests. If you send a patch, - remember to update the corresponding unit tests. If fact, I prefer - new feature to be submitted in the form of new unit tests. - -For other information, feel free to ask on the rubyonrails-talk -(http://groups.google.com/group/rubyonrails-talk) mailing list. |