The document discusses ActiveRecord in Rails for interacting with database tables. It explains that every model class corresponds to a database table, and Rails generates migrations that create the tables. It demonstrates using the Rails console to find and load records from a table. Dynamic getter and setter methods allow accessing column values. ActiveRecord handles saving, updating, and querying records while protecting against SQL injection attacks.

1. ACTIVERECORD
Rails 3

2. MVC

3. MODEL CLASS
in app/models/person.rb
class Message < ActiveRecord::Base
end

4. EVERY MODEL
HAS
A CORRESPONDING
DATABASE TABLE

5. MVC

6. HOW DID WE
GET
A DATABASE TABLE?

7. RUBY-DRIVEN SCHEMA
• scaffold generates
db/migrate/20110131021702_create_people.rb
• rake db:migrate
runs the migration, creates the table
• Watch what we did before in slow motion...

8. DEMO

9. RAILS CONSOLE
>> ActiveRecord::Base.logger = Logger.new(STDOUT)

10. RAILS CONSOLE
>> ActiveRecord::Base.logger = Logger.new(STDOUT)
>> Person.first
SQL (1.0ms) SELECT name
FROM sqlite_master
WHERE type = 'table' AND NOT name = 'sqlite_sequence'
Person Load (1.0ms) SELECT "people".* FROM "people" LIMIT 1
=> #<Person id: 2, first_name: "Wilma", last_name: "Flinstone",
created_at: "2010-10-19 19:59:36", updated_at: "2010-10-19
19:59:36">

11. RAILS CONSOLE
>> ActiveRecord::Base.logger = Logger.new(STDOUT)
>> Person.first
SQL (1.0ms) SELECT name
FROM sqlite_master
WHERE type = 'table' AND NOT name = 'sqlite_sequence'
Person Load (1.0ms) SELECT "people".* FROM "people" LIMIT 1
=> #<Person id: 2, first_name: "Wilma", last_name: "Flinstone",
created_at: "2010-10-19 19:59:36", updated_at: "2010-10-19
19:59:36">
find "people" table name

12. RAILS CONSOLE
>> ActiveRecord::Base.logger = Logger.new(STDOUT)
>> Person.first
SQL (1.0ms) SELECT name
FROM sqlite_master
WHERE type = 'table' AND NOT name = 'sqlite_sequence'
Person Load (1.0ms) SELECT "people".* FROM "people" LIMIT 1
=> #<Person id: 2, first_name: "Wilma", last_name: "Flinstone",
created_at: "2010-10-19 19:59:36", updated_at: "2010-10-19
19:59:36">
find first row in "people table"

13. DYNAMIC GETTERS AND
SETTERS
>> bret = Person.new
>> bret.first_name = "Bret"
>> bret.last_name = "Smith"
>> bret.first_name
"Bret"
>> bret.xxx
NoMethodError

14. MORE ACTIVE RECORD
• save to database as needed
• automatically handle update/insert
• dynamic queries

15. SQL INJECTION

16. SAFE FROM SQL INJECTION
class 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

17. QUESTIONS?