The document discusses DataMapper, an ORM (object-relational mapper) library for Ruby. It describes how DataMapper allows for declarative mapping of objects to a database, automatic migrations and validations, complex queries, custom adapters, and embedded values. Examples are provided throughout to demonstrate DataMapper's features like migrations, associations, queries, and more.

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

4. Why?

5. Declarative

6. class Person
include DataMapper::Resource
property :id, Serial
property :name, String, :required => true
property :age, Integer
end

7. Automatic
migrations

8. DataMapper.auto_migrate!
DataMapper.auto_upgrade!

9. Storage
constraints

10. class Person
include DataMapper::Resource
property :id, Serial
property :name, String, :required => true
property :age, Integer
end

11. class Person
include DataMapper::Resource
property :id, Serial
property :name, String, :required => true
property :age, Integer
end
CREATE TABLE "people" ("id" SERIAL NOT NULL,
"name" VARCHAR(50) NOT NULL,
"age" INTEGER, PRIMARY KEY("id"))

12. class Person
include DataMapper::Resource
property :id, Serial
property :name, String, :required => true
property :age, Integer
has n, :addresses, :constraint => :destroy!
end

13. class Person
include DataMapper::Resource
property :id, Serial
property :name, String, :required => true
property :age, Integer
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

14. Automatic
validations

15. class Person
include DataMapper::Resource
property :id, Serial
property :name, String, :required => true
property :age, Integer
end

16. class Person
include DataMapper::Resource
property :id, Serial
property :name, String, :required => true
property :age, Integer
end
person = Person.create
person.errors => #<DataMapper::Validations::ValidationErrors:0x101d217a0
@errors={:name=>["Name must not be blank"]},
@resource=#<Person @id=nil @name=nil @age=nil>>

18. http://www.flickr.com/photos/jon_truran

19. Convenience

20. "that just pisses me off"

21. Lazyness

22. people = Person.all
~ Query log empty...

23. people = Person.all
~ Query log empty...
p people
~ SELECT "id", "name" FROM people

24. :each

25. people = Person.all
people.each do |person|
p person.addresses
end

26. 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))

27. Complex
queries

28. Person.all(:addresses => {:street.like => "%street%"})

29. Person.all(: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"

30. class Person
include DataMapper::Resource
...
def self.named_like_me
all(:name.like => "%me%")
end
end

31. class Person
include DataMapper::Resource
...
def self.named_like_me
all(:name.like => "%me%")
end
end
Person.named_like_me.all(:age.gt => 27)
~ SELECT "id", "name", "age" FROM "people"
WHERE ("name" LIKE '%me%' AND "age" > 27) ORDER BY "id"

32. Person.all(:name.like => '%me%').addresses.all(:street.not => nil)

33. 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"

34. Person.all - Person.all(:name => 'Dan Kubb')

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

36. Not SQL centric

37. DataMapper.setup(:default, "postgres://postgres@localhost/dm")
DataMapper.setup(:docs, "mongo://user@localhost/dm")

38. class Post
include DataMapper::Resource
has n, :audits
end
class Audit
include DataMapper::Resource
def self.default_repository_name
:log
end
end

39. Custom
adapters

40. 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

41. Future

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

44. drops into2008
Back to Rails
1.0

46. 1.8 / 1.9
(on Windows too)

47. Dan Kubb
Martin Gamsjaeger

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