ActiveRecord::Base

Cur$s  Schofield

$ rails new ar_ex

$ rails -v

3.0.3

Edit Gemfile

source 'http://rubygems.org' gem ‘rails’,‘3.0.3’ gem ‘rspec-rails’ gem ‘sqlite3-ruby’, :require => ‘sqlite’

$ bundle

$ rails g rspec:install

$ rails g model Message body:text public_key:text

invoke rspec

create spec/models/message_spec.rb

require 'spec_helper'

describe Message do pending "a class in itself"end

invoke active_record

create db/migrate/20110208201036_create_messages.rb

class CreateMessages < ActiveRecord::Migration def self.up # rake db:migrate end def self.down # rake db:migrate:down VERSION=file_name # rake db:migrate:redo VERSION=file_name endend

create_table :messages do |t| t.text :body t.text :public_key

t.timestamps end

rails g model Message body:text public_key:text

drop_table :messages

http://apidock.com/rails/ActiveRecord/ConnectionAdapters/SchemaStatements

create app/models/message.rb

class Message < ActiveRecord::Baseend

Where are the methods?

$ rails console

> Message.new

ActiveRecord::StatementInvalid:

Could not find table 'messages'

from /Users/o_o/.rvm/gems/ruby-1.9.2-p0@rails3/gems/activerecord-3.0.3/lib/active_record/connection_adapters/sqlite_adapter.rb:295:in `table_structure'

every model has a corresponding database table

$ rails db

PRAGMA table_info(messages);

nothing!

.quit;

$ rake db:migrate

$ rails db

PRAGMA table_info(messages);

0|id|INTEGER|1||11|body|text|0||02|public_key|text|0||03|created_at|datetime|0||04|updated_at|datetime|0||0

.quit

$ rails console

> Message.new

=> #<Message id: nil, body: nil, public_key: nil, created_at: nil, updated_at: nil>

>msg = Message.new>msg.body = 2>msg.save>msg

=> #<Message id: 1, body: 2, public_key: nil, created_at: "2011-02-08 20:56:33", updated_at: "2011-02-08 20:56:33">

> msg.body.class

=> Fixnum

> Message.find(1)

=> #<Message id: 1, body: "2", public_key: nil, created_at: "2011-02-08 20:56:33", updated_at: "2011-02-08 20:56:33">

> Message.find(1).body.class

=> String

> Message.find(1).updated_at.class

=> ActiveSupport::TimeWithZone

With Great Power Comes With Great Responsibility

One more time..

$ rails console

> ActiveRecord::Base.logger=Logger.new($stdout)

> Message.new.save

SQL (0.3ms) SELECT name FROM sqlite_master WHERE type = 'table' AND NOT name = 'sqlite_sequence'

AREL (0.5ms) INSERT INTO "messages" ("body", "public_key", "created_at", "updated_at") VALUES (NULL, NULL, '2011-02-09 01:55:09.111181', '2011-02-09 01:55:09.111181')

> exit

Active Record Features

validationshttp://apidock.com/rails/v3.0.0/ActiveModel/Validations

before_save

http://apidock.com/rails/v3.0.0/ActiveRecord/Callbacks

scopeshttp://apidock.com/rails/v3.0.0/ActiveRecord/NamedScope/

ClassMethods/scope

Understanding is free with practice - Without practice understanding cannot stand.