This document provides an overview of DataMapper, an object-relational mapper (ORM) library for Ruby applications. It summarizes DataMapper's main features such as associations, migrations, database adapters, naming conventions, validations, custom types and stores. The document also provides examples of how to use DataMapper with different databases, import/export data, and validate models for specific contexts.

1. datamapper
the persistence framework

2. who am I?

3. (Booth 501)

4. DataMapper

5. datamapper

6. object relational
mapper

7. like activerecord

8. like activerecord
★ DB adapters ★ many-to-many
★ migrations ★ -through
★ associations ★ polymorphic
★ one-to-one ★ lifecycle events
★ one-to-many ★ sti
★ many-to-one ★ etc.

9. drops into Rails
1.0

10. (or merb)
0.9

11. architecture
Application Merb Rails
DataMapper
Adapters DO.rb YAML IMAP
Data Stores

12. some caveats

13. work in progress
0.9 1.0

14. be prepared for code

15. why did we build it?

16. identity map

18. Foo[1] Foo
id = 1
Foo[1] ...

19. foo[1] == foo[1]
#=> true

20. loadedset

21. foo.all
Foo Foo Foo Foo Foo Foo
id = 1 id = 2 id = 3 id = 4 id = 5 id = 6
... ... ... ... ... ...
LoadedSet

22. composite keys

23. belongs_to :project,
:child_key => [:name, :tag]

24. legacy data

25. naming conventions
(yours)

26. naming conventions
underscored
foo::barBaz => foo/bar_baz

27. naming conventions
underscoredandpluralized
foo::barBaz => foo_bar_bazs

28. naming conventions
underscoredandpluralizedwithoutmodule
foo::barBaz => bazs

29. naming conventions
yaml
foo::Bar => foo/bars.yaml

30. support for multiple
databases
(even in the same model)

31. Post.all(:repository => :legacy)
Post.all
# :repository => :default

32. prepared statements
1.0

33. custom types

34. embedded values
1.0

35. Employments Employment
id: int id<Integer>
person_id: int
person<Person>
start: date
end: date start<Date>
salary_amt: dec
end<Date>
salary_cur: char
salary<Money>

36. declared properties
property :id, :key => true

37. robust queries

38. Child.all(
“mother.last_name.like” =>
“Jane%”,
:name.like => “Jim”
)

39. dirty tracking

40. modularity

41. unified interface for
drivers

42. •connections
• commands
• readers
• cursors (forward-only)
• quoting
• transactions

43. Connection Connection Connection Connection Connection
Connection Pool
create_command “select * from foos where id = ?”
Command
execute_reader Reader next values next ...
execute_reader(12) =>
select * from foos where id = 12

44. works today on:
mysql, sqlite, postgres

45. fast, written in C

46. simple interface for
adapters

47. •read by key
• read by query
• update by key
• update set
• delete
• (optional: transactions)

48. salesforce adapter in
200 LOC

49. Errors
Operators
Naming
Conventions
~/.salesforce
Build Query
Load Result Set
Similar CRUD
Demo

50. what does it look like?

51. Zoo.all(
:age.gt => 30,
:name.not =>
[“bob”, “jones”]
)

52. SELECT
“age”, “name”, “description”
FROM “zoos”
WHERE
(“age” > 30) AND
(“name” NOT IN
(“bob”, “jones”))

53. Zoo.first.eql? Zoo.first
#=> true

54. Zoo.all.map {|x| x.animals }
how many queries?
2

55. we call this
strategic eager loading.

56. lazy loading

57. class Post
include DataMapper::Resource
property :id, Fixnum,
:serial => true
property :title, String
property :body, Text,
:lazy => true
end

58. posts = Post.all
SELECT “id”, “title”
FROM “posts”

59. return two objects
ids 1 and 2

60. posts.first.body
SELECT “body”
FROM “posts”
WHERE (“id” IN (1,2))

61. posts.map{|x| x.body}
SELECT “body”
FROM “posts”
WHERE (“id” IN (1,2))

62. lazy loaded grouping

63. class Post
include DataMapper::Resource
property :id, Fixnum,
:serial => true
property :title, String,
:lazy => [:details]
property :body, Text,
:lazy => [:details]
end

64. you can go off the
golden path

65. class Post
include DataMapper::Resource
property :title, String
repository(:legacy) do
property :title, String,
:field => “T1tLz”
end
end

66. Post.all(:repository => :legacy)
repository(:legacy) do
Post.all
end

67. Post.all
Post.all(:repository =>
:default)
repository(:default) do
Post.all
end

68. naming conventions
repository(:legacy).adapter.
resource_naming_convention =
DM::
NamingConventions::
Underscored AndPluralized

69. naming conventions
repository(:legacy).adapter.
resource_naming_convention =
lambda do |klass|
“tbl#{klass.camel_case}”
end

70. default repository
class Post
include DataMapper::Resource
def self.default_repository_name
:legacy
end
end

71. import data
Post.copy(:legacy, :default)
Post.copy(:legacy, :default,
:created_at.gt =>
Date.today - 365)
1.0

72. import data
class Post
property :title, String
repository(:legacy) do
property :title, String,
:field => “TIT13”
end
end

73. custom types

74. primitives
Trueclass, string, text, float, fixnum,
bigdecimal, datetime, date, object, class

75. custom types
class Post
include DataMapper::Resource
property :title, String
property :author, FullName
property :details, Csv
end

76. class FullName < DM::Type
primitive String
size 100
def self.load(str)
str.split(“, ”).reverse
end
def self.dump(ary)
ary.reverse.join(“, ”)
end
end

77. class Csv < DM::Type
primitive String
size 65355
def self.load(str)
FasterCSV.parse(value)
end
def self.dump(ary)
FasterCSV.generate do |csv|
ary.each {|line| csv << line}
end
end
end

78. Post.create!(
:title => “New Post”,
:author => [“Yehuda”, “Katz”],
:metadata => [
[“Some”, “Sample”, “Data”],
[“More”, “Sample”, “Data”]
]
)

79. in the database
Title “New Post”
Author “Katz, Yehuda”
“Some,Sample,Datan
Metadata
More,Sample,Datan”

80. and it’s lazy-parsed

81. custom stores

82. stores are uris

83. mysql://user@localhost

84. setting up
DataMapper.setup(
:default,
“mysql://user@localhost”
)

85. database.yml
development:
default:
adapter: mysql
database: app_dev
user: person
password: sekrit

86. database.yml
legacy:
adapter: sqlite3
database: config/l3g.db

87. yaml:///fixtures
1.0

88. ssh+yaml://
fixtures.engineyard.com/
fixtures
1+

89. database.yml
test:
default:
adapter: yaml
database: app_test.db
legacy:
adapter: yaml
database: l3g_test.db

90. making fixtures
Post.copy(:default, :fixtures)
rake db:copy_fixtures

91. validations

92. class Product
include DataMapper::Resource
property :title, String
property :price, String,
validates_length_of
:nullable => false,
:validation_context =>
validates_presence_of
:purchase
end valid_for_purchase?

93. class Product
include DataMapper::Resource
property :title, String
property :number, String,
:format =>
/d{3}-[a-zA-Z]{9}-0/
end validates_format_of

94. class Product
include DataMapper::Resource
property :title, String
property :number, String,
:format => proc {|n|
n.split(“-”).size == 2}
validates_format_of
end

95. class Product
include DataMapper::Resource
property :title, String
property :number, String,
:length => 2..10,
:validation_context =>
validates_length_of
:import
valid_for_import?
save(:import)
end

96. class Product
include DataMapper::Resource
property :title, String
property :number, String,
validates_length_of :number,
:in => (2..10),
:when => :import
end valid_for_import?

97. thank you.

98. any questions?

99. </railsconf>