Active Record Introduction - 3

ACTIVERECORDRails 3

Sunday, November 13, 11

MVC


MODEL CLASS

in app/models/person.rb

class Message < ActiveRecord::Base

end


EVERY MODELHAS

A CORRESPONDING DATABASE TABLE


MVC


HOW DID WEGET

A DATABASE TABLE?


RUBY-DRIVEN SCHEMA

• scaffold generatesdb/migrate/20110131021702_create_people.rb

• rake db:migrate runs the migration, creates the table

•


DEMO


$ rails new ar_ex


$ rails -v


Edit Gemfile


source 'http://rubygems.org' gem ‘rails’ gem ‘rspec-rails’ gem ‘sqlite3’


http://rubygems.org

http://rubygems.org

$ 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.change # rake db:migrate end 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:textSunday, November 13, 11

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


One more time..


$ rails console


> Message.create!


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/v3.1.0/ActiveModel/Validations


http://apidock.com/rails/v3.1.0/ActiveModel/Validations

http://apidock.com/rails/v3.1.0/ActiveModel/Validations

before_save

http://apidock.com/rails/v3.1.0/ActiveRecord/Callbacks




scopeshttp://apidock.com/rails/v3.1.0/ActiveRecord/NamedScope/

ClassMethods/scope


http://apidock.com/rails/v3.0.0/ActiveRecord/NamedScope/ClassMethods/scope




SQL INJECTION


SAFE FROM SQL INJECTIONclass User < ActiveRecord::Base

def self.authenticate_unsafely(user_name, password) find(:first, :conditions =>

"user_name = '#{user_name}' AND password = '#{password}'")

end

def self.authenticate_safely(user_name, password)

find(:first, :conditions => [ "user_name = ? AND password = ?", user_name, password ])

end

def self.authenticate_safely_simply(user_name, password)

find(:first, :conditions =>

{ :user_name => user_name, :password => password })

end


QUESTIONS?


Technology

Active Record Introduction - 3