This document provides an overview of the DataMapper ORM library for Ruby. It discusses DataMapper 0.10 being released after 11 months of work. It demonstrates basic usage like defining models with properties and relationships. It also covers more advanced features like querying, custom types, embedded documents, validation, timestamps, constraints and plugins. Contact information is provided at the end for the DataMapper project on GitHub, mailing list and IRC channel to ask any questions.

1. Dirkjan Bussink
http://github.com/dbussink
http://twitter.com/dbussink

3. ORM?

4. DataMapper 0.10 is Released
DataMapper 0.10 is ready for release. We’ve worked on it
for the past 11 months, pushed 1250 commits, written
3000+ specs, and fixed 140 tickets in the process.

5. 1.8
1.9
JRuby
Windows *
* Sorry, no Windows / 1.9 yet...

7. Dan Kubb

8. DataMapper 101

9. class Person
include DataMapper::Resource
property :id, Serial
property :name, String
property :age, Integer
end

10. DataMapper.auto_migrate!
DataMapper.auto_upgrade!

12. class Person
...
property :name, String, :length => 512
...
end

13. Person.all(:name.like => "%me%")
Ruby!

14. repository do
puts Person.get(1).object_id => 2232427080
puts Person.get(1).object_id => 2232427080
end
Identity Map

16. Pluggable
Identity Map

17. http://www.flickr.com/photos/mattimattila

18. people = Person.all(:name.like => "%me%")
~ Query log empty...
p people
~ SELECT "id", "name" FROM people

19. :each
Kicker

20. people = Person.all
people.each do |person|
p person.addresses
end
SELECT "id", "name" FROM people;
SELECT "id", "street" FROM addresses WHERE ("person_id" IN (1,2,3))
Eager loading

21. RDBMS
IMAP
YAML

22. DataMapper.setup(:repo1, "postgres://postgres@localhost/dm")
DataMapper.setup(:repo2, "mysql://root@localhost/dm")
repository(:repo1) do
p Person.get(1) => #<Person @id=1 @name="Dirkjan" @age=27>
end
repository(:repo2) do
p Person.get(1) => #<Person @id=1 @name="Dan" @age=35>
end
Multiple repositories

23. DataMapper.setup(:repo1, "postgres://postgres@localhost/dm")
DataMapper.setup(:repo2, "mysql://root@localhost/dm")
get "/" do
# Odd / even sharding
repo = "repo#{user.id % 2 + 1}".to_sym
repository(repo) do
@people = Person.all
end
erb :people
end
Simple sharding

24. module DataMapper
module Adapters
class MyStorageAdapter < AbstractAdapter
def create(resources)
end
def read(query)
end
def update(attributes, collection)
end
def delete(collection)
end
end
end
end

25. Person.all(:name.like => 'dirk%').update!(:age => 28)
Person.all.destroy!(:age.gte => 100)
Bulk updates

26. When simple
querying is
not enough

27. Person.all(Person.addresses.street.like => "%street%")
SELECT "people"."id", "people"."name", "people"."age" FROM "people"
INNER JOIN "addresses" ON "people"."id" = "addresses"."person_id"
WHERE "addresses"."street" LIKE '%street%'
GROUP BY "people"."id", "people"."name", "people"."age"
ORDER BY "people"."id"
Complex querying!

28. class Person
include DataMapper::Resource
property :id, Serial
property :name, String
property :age, Integer
has n, :addresses
def self.named_like_me
all(:name.like => "%me%")
end
def self.older_than_me
all(:age.gt => 27)
end
end
Person.named_like_me.older_than_me
~ SELECT "id", "name", "age" FROM "people"
WHERE ("name" LIKE '%me%' AND "age" > 27) ORDER BY "id"
Query chaining

29. class Person
s
include DataMapper::Resource
e
property :id, Serial
p
property :name, String
o y
property :age, Integer
c b
s u
has n, :addresses
d R
def self.named_like_me
e
all(:name.like => "%me%")
end
m in
a la
def self.older_than_me
all(:age.gt => 27)
N p
end
end
i n
Person.named_like_me.older_than_me
~ SELECT "id", "name", "age" FROM "people"
WHERE ("name" LIKE '%me%' AND "age" > 27) ORDER BY "id"
Query chaining

30. Person.all(:name.like => '%me%').addresses.all(:street.not => nil)
SELECT "id", "street", "person_id" FROM "addresses"
WHERE (
"person_id" IN (SELECT "id" FROM "people" WHERE "name" LIKE '%me%')
AND "street" IS NOT NULL
) ORDER BY "id"
Subqueries

32. Person.all - Person.all(:name => 'Dan Kubb')
SELECT * FROM people WHERE NOT(name = 'Dan Kubb')

33. [1, 2] & [2, 3] == [2]
[1, 2] | [2, 3] == [1, 2, 3]

34. Plugins

35. class Person
...
property :name, String, :nullable => false
end
CREATE TABLE "people" ("id" SERIAL NOT NULL,
"name" VARCHAR(50) NOT NULL,
"age" INTEGER, PRIMARY KEY("id"))
Automatic Validations

36. Person.create
DataObjects::IntegrityError: ERROR:
null value in column "name" violates not-null constraint

37. person = Person.create
p person.errors => #<DataMapper::Validate::ValidationErrors:0x101d217a0
@errors={:name=>["Name must not be blank"]},
@resource=#<Person @id=nil @name=nil @age=nil>>

38. class Person
...
validates_present :name
end
Validations

39. class Person
...
property :created_at, DateTime
property :updated_at, DateTime
end
Timestamps

40. Person.all.adjust!(:age => 1)
Adjustments

41. class Person
...
has n, :addresses, :constraint => :destroy!
end
ALTER TABLE addresses
ADD CONSTRAINT addresses_person_id_fk
FOREIGN KEY (person_id)
REFERENCES people
ON DELETE CASCADE
ON UPDATE CASCADE
Constraints

42. module DataMapper
module Types
class IPAddress < DataMapper::Type
primitive String
length 16
def self.load(value, property)
IPAddr.new(value)
end
def self.dump(value, property)
value.to_s
end
def self.typecast(value, property)
value.kind_of?(IPAddr) ? value : load(value, property)
end
end
end
end
class NetworkNode
...
property :ipaddress, IPAddress
end
Custom types

44. class Address
include DataMapper::EmbeddedValue
property :street, String
end
class Person
include DataMapper::Resource
property :id, Serial
property :name, String
has n, :addresses
end

45. User.select { |u| u.id == 1 && u.name == 'Dan Kubb' }
Ambition style queries

46. http://www.flickr.com/photos/zoomar

47. http://datamapper.org/
http://github.com/datamapper
http://groups.google.com/group/datamapper
irc://irc.freenode.net/#datamapper

48. Questions?