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DataMapper 2 an object mapping toolkit RubyShift Conference, Kiev 2012 Monday, October 1, 12

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Hi I’m solnic! • Software Consultant • DataMapper Core Team • Blog at solnic.eu • Hack at github.com/solnic • Tweet @_solnic_ Monday, October 1, 12

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Active Record vs Data Mapper Monday, October 1, 12

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Active Record • Simple pattern • Designed for simple use cases when business logic is not complex (ie CRUD) • No separation between persistence and domain objects • 1:1 mapping between db schema and domain objects Monday, October 1, 12

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Data Mapper • Advanced system implementing various patterns (Mapper, Unit of Work, Repository) • Strict separation between persistence and domain logic • Designed for cases where mixing persistence concerns with domain logic becomes a problem Monday, October 1, 12

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Active Record Data Mapper vs Monday, October 1, 12

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Active Record Data Mapper vs Monday, October 1, 12

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Active Record Data Mapper & Monday, October 1, 12

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What went wrong with ActiveRecord in Rails Monday, October 1, 12

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class User < ActiveRecord::Base end Active Record in Rails Monday, October 1, 12

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Active Record in Rails (User.methods.sort - Object.methods.sort).count # => 391 391 new public class methods... Monday, October 1, 12

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ActiveRecord in Rails Does TOO MUCH Monday, October 1, 12

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• Persistence • Validations • Life cycle hooks • Typecasting • Mass-assignment security • ...and much much more! ActiveRecord in Rails Monday, October 1, 12

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DataMapper 2 Monday, October 1, 12

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DataMapper 2 Repository Mapper & Session Domain Model Monday, October 1, 12

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Domain Model Monday, October 1, 12

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Domain Model class User attr_reader :id, :name, :age def initialize(attributes) @id, @name, @age = attributes.values_at(:id, :name, :age) end # business logic goes here :) end Monday, October 1, 12

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Domain Model require './user' require 'rspec' describe User do subject { User.new(id: 1, name: 'Jane', age: 21) } describe '#name' do its(:name) { should eql('Jane') } end describe '#age' do its(:age) { should eql(21) } end end Monday, October 1, 12

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Mapper Monday, October 1, 12

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Mapper class User attr_reader :id, :name, :age def initialize(attributes) @id, @name, @age = attributes.values_at(:id, :name, :age) end # business logic goes here :) end Monday, October 1, 12

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Mapper class UserMapper < DataMapper::Mapper::Relation::Base model User relation_name :users repository :postgres map :id, Integer, :key => true map :name, String, :to => :username map :age, Integer end Monday, October 1, 12

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Mapper class User include DataMapper::Model attribute :id, Integer attribute :name, String attribute :age, Integer end DataMapper.generate_mapper_for(User) do key :id map :name, :to => :username end Monday, October 1, 12

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Mapper DataMapper[User].all DataMapper[User].order(:age) DataMapper[User].one(name: 'Jane') DataMapper[User].find(age: 18) Monday, October 1, 12

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Mapper class Address include DataMapper::Model attribute :id, Integer attribute :street, String attribute :city, String attribute :zipcode, String end class User include DataMapper::Model attribute :id, Integer attribute :name, String attribute :age, Integer attribute :address, Address end Monday, October 1, 12

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Mapper class Address include DataMapper::Model attribute :id, Integer attribute :street, String attribute :city, String attribute :zipcode, String end class User include DataMapper::Model attribute :id, Integer attribute :name, String attribute :age, Integer attribute :address, Address end a user has an address Monday, October 1, 12

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Mapper DataMapper.generate_mapper_for(Address) do key :id end DataMapper.generate_mapper_for(User) do key :id map :name, :to => :username has 1, :address, Address end Monday, October 1, 12

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Mapper DataMapper.generate_mapper_for(Address) do key :id end DataMapper.generate_mapper_for(User) do key :id map :name, :to => :username has 1, :address, Address end OneToOne Relationship Monday, October 1, 12

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Mapper user = DataMapper[User].include(:address).first user.address.city user.address.street user.address.zipcode Monday, October 1, 12

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Mapper class Order include DataMapper::Model attribute :id, Integer attribute :product, String end class User include DataMapper::Model attribute :id, Integer attribute :name, String attribute :age, Integer attribute :orders, Array[Order] end Monday, October 1, 12

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Mapper class Order include DataMapper::Model attribute :id, Integer attribute :product, String end class User include DataMapper::Model attribute :id, Integer attribute :name, String attribute :age, Integer attribute :orders, Array[Order] end a user has orders Monday, October 1, 12

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Mapper DataMapper.generate_mapper_for(Order) do key :id end DataMapper.generate_mapper_for(User) do key :id map :name, :to => :username has 0..n, :orders, Order end DataMapper[User].include(:orders).all Monday, October 1, 12

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Mapper DataMapper.generate_mapper_for(Order) do key :id end DataMapper.generate_mapper_for(User) do key :id map :name, :to => :username has 0..n, :orders, Order end DataMapper[User].include(:orders).all OneToMany Relationship Monday, October 1, 12

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Session Work In Progress... Monday, October 1, 12

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Session DataMapper.session do |session| user = User.new(name: 'Piotr', age: 28) session.persisted?(user) # => false session.insert(user) session.commit end Monday, October 1, 12

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Session DataMapper.session do |session| user = User.new(name: 'Piotr', age: 28) session.persisted?(user) # => false session.insert(user) session.commit end is the user persisted? Monday, October 1, 12

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Session DataMapper.session do |session| user = User.new(name: 'Piotr', age: 28) session.persisted?(user) # => false session.insert(user) session.commit end queue the user to be persisted Monday, October 1, 12

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Session DataMapper.session do |session| user = User.new(name: 'Piotr', age: 28) session.persisted?(user) # => false session.insert(user) session.commit end write changes to the database Monday, October 1, 12

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Session DataMapper.session do |session| user = session[User].get(1) user.age = 29 session.dirty?(user) # => true session.update(user) session.commit end Monday, October 1, 12

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Session DataMapper.session do |session| user = session[User].get(1) user.age = 29 session.dirty?(user) # => true session.update(user) session.commit end fetch the user and track it Monday, October 1, 12

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Session DataMapper.session do |session| user = session[User].get(1) user.age = 29 session.dirty?(user) # => true session.update(user) session.commit end was the user changed? Monday, October 1, 12

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Session DataMapper.session do |session| user = session[User].get(1) user.age = 29 session.dirty?(user) # => true session.update(user) session.commit end update the user in the database Monday, October 1, 12

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Session DataMapper.session do |session| user = User.new(name: 'Piotr', age: 28) address = Address.new( street: 'Street 1', city: 'Krakow', zipcode: '12345' ) user.address = address session.insert(user) session.commit end Monday, October 1, 12

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Session DataMapper.session do |session| user = User.new(name: 'Piotr', age: 28) address = Address.new( street: 'Street 1', city: 'Krakow', zipcode: '12345' ) user.address = address session.insert(user) session.commit end assign the address to the user Monday, October 1, 12

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Session DataMapper.session do |session| user = User.new(name: 'Piotr', age: 28) address = Address.new( street: 'Street 1', city: 'Krakow', zipcode: '12345' ) user.address = address session.insert(user) session.commit end queue the user to be persisted Monday, October 1, 12

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Session DataMapper.session do |session| user = User.new(name: 'Piotr', age: 28) address = Address.new( street: 'Street 1', city: 'Krakow', zipcode: '12345' ) user.address = address session.insert(user) session.commit end write both objects to the database Monday, October 1, 12

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Repository Monday, October 1, 12

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Veritas Powerful Relational Algebra Library Monday, October 1, 12

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Veritas • Created by Dan Kubb in 2010 • Complete support for all relational algebra operations • All operations can be run in-memory • Can be extended to support any kind of a datastore • Can be used with multiple different databases Monday, October 1, 12

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Repository class User include DataMapper::Model attribute :id, Integer attribute :name, String attribute :age, Integer end DataMapper.generate_mapper_for(User) do key :id map :name, :to => :username end Monday, October 1, 12

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Repository mapper = DataMapper[User] mapper.relation.class # => Veritas::Relation::Gateway mapper.relation.header.to_set.map { |a| [ a.name, a.type ] } # => [ # [ :id, Veritas::Attribute::Integer ], # [ :username, Veritas::Attribute::String ], # [ :age, Veritas::Attribute::Integer ] # ] mappers wrap veritas gateway relations Monday, October 1, 12

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Repository mapper = DataMapper[User] relation = Veritas::Relation.new( mapper.relation.header, [ [ 1, 'John', 18 ], [ 2, 'Jane', 21 ] ] ) relation.restrict { |r| r.age.gt(18) }.each do |tuple| puts tuple[:username] # => 'Jane' end building an in-memory relation Monday, October 1, 12

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Repository user_mapper = DataMapper[User] address_mapper = DataMapper[Address] user_relation = Veritas::Relation.new( user_mapper.relation.header, [ [ 1, 'John', 18 ], [ 2, 'Jane', 21 ] ]) address_relation = Veritas::Relation.new( address_mapper.relation.header, [ [ 1, 1, 'Street 1', '12345' ], [ 2, 2, 'Street 2', '54321' ] ]) joining two relations in-memory Monday, October 1, 12

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Repository user_address = user_relation.rename(:id => :user_id). join(address_relation) user_address.restrict { |r| r.street.eq('Street 1') }. each do |tuple| puts tuple[:username] # => "John" end joining two relations in-memory Monday, October 1, 12

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Projects on Github • github.com/dkubb/veritas • github.com/solnic/virtus • github.com/solnic/dm-mapper • github.com/solnic/dm-session Monday, October 1, 12

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Thank You! Time for questions? Monday, October 1, 12