Blazing Cloud Rails class. details on the 'rails generate model' command.

1. ActiveRecord::Base
Cur$s
Schofield

2. $ rails new ar_ex

3. $ rails -v
3.0.3

4. Edit Gemfile

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

6. $ bundle

7. $ rails g rspec:install

8. $ rails g model Message
body:text public_key:text

9. invoke rspec

10. create spec/models/
message_spec.rb

11. require 'spec_helper'
describe Message do
pending "a class in itself"
end

12. invoke active_record

13. create db/migrate/
20110208201036_create_messages.rb

14. 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
end
end

15. create_table :messages do |t|
t.text :body
t.text :public_key
t.timestamps
end
rails g model Message body:text public_key:text

16. drop_table :messages

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

18. create app/models/message.rb

19. class Message < ActiveRecord::Base
end

20. Where are the methods?

21. $ rails console

22. > Message.new

23. 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'

24. every model has a corresponding
database table

25. $ rails db

26. PRAGMA table_info(messages);

27. nothing!

28. .quit;

29. $ rake db:migrate

30. $ rails db

31. PRAGMA table_info(messages);

32. 0|id|INTEGER|1||1
1|body|text|0||0
2|public_key|text|0||0
3|created_at|datetime|0||0
4|updated_at|datetime|0||0

33. .quit

34. $ rails console

35. > Message.new

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

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

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

39. > msg.body.class

40. => Fixnum

41. > Message.find(1)

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

43. > Message.find(1).body.class

44. => String

45. > Message.find(1).updated_at.class

46. => ActiveSupport::TimeWithZone

47. With Great Power Comes With
Great Responsibility

48. One more time..

49. $ rails console

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

51. > Message.new.save

52. 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')

53. > exit

54. Active Record Features

55. validations
http://apidock.com/rails/v3.0.0/ActiveModel/Validations

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

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

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