Datamapper @ Railsconf2010

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

Declarative

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

Automatic migrations

DataMapper.auto_migrate! DataMapper.auto_upgrade!

Storage constraints

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"))

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

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

Automatic validations

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>>

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

Convenience

"that just pisses me off"

Lazyness

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

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

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

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))

Complex queries

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

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"

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

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"

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

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"

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

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

Not SQL centric

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

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

Custom adapters

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

Future

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

drops into2008 Back to Rails 1.0

1.8 / 1.9 (on Windows too)

Dan Kubb Martin Gamsjaeger

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

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Datamapper @ Railsconf2010

by Dirkjan Bussink

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