DataMapper 2 - an object mapping toolkit

An introduction to the DataMapper 2 stack.

Transcript

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

   View Slide

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

   View Slide

3. Active Record
   vs
   Data Mapper
   Monday, October 1, 12
   

   View Slide

4. 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
   

   View Slide

5. 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
   

   View Slide

6. Active Record
   Data Mapper
   vs
   Monday, October 1, 12
   

   View Slide

7. Active Record
   Data Mapper
   vs
   Monday, October 1, 12
   

   View Slide

8. Active Record
   Data Mapper
   &
   Monday, October 1, 12
   

   View Slide

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

   View Slide

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

    View Slide

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

    View Slide

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

    View Slide

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

    View Slide

14. DataMapper 2
    Monday, October 1, 12
    

    View Slide

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

    View Slide

16. Domain Model
    Monday, October 1, 12
    

    View Slide

17. 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
    

    View Slide

18. 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
    

    View Slide

19. Mapper
    Monday, October 1, 12
    

    View Slide

20. 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
    

    View Slide

21. 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
    

    View Slide

22. 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
    

    View Slide

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

    View Slide

24. 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
    

    View Slide

25. 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
    

    View Slide

26. 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
    

    View Slide

27. 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
    

    View Slide

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

    View Slide

29. 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
    

    View Slide

30. 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
    

    View Slide

31. 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
    

    View Slide

32. 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
    

    View Slide

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

    View Slide

34. 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
    

    View Slide

35. 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
    

    View Slide

36. 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
    

    View Slide

37. 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
    

    View Slide

38. 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
    

    View Slide

39. 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
    

    View Slide

40. 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
    

    View Slide

41. 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
    

    View Slide

42. 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
    

    View Slide

43. 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
    

    View Slide

44. 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
    

    View Slide

45. 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
    

    View Slide

46. Repository
    Monday, October 1, 12
    

    View Slide

47. Veritas
    Powerful Relational Algebra Library
    Monday, October 1, 12
    

    View Slide

48. 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
    

    View Slide

49. 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
    

    View Slide

50. 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
    

    View Slide

51. 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
    

    View Slide

52. 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
    

    View Slide

53. 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
    

    View Slide

54. 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
    

    View Slide

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

    View Slide