Beyond the ORM - RuLu Conf 2012

Transcript

1. Beyond the ORM
   an introduction to DataMapper 2
   RuLu 2012
   Sunday, June 24, 12
   

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2. Piotr Solnica
   • codebenders.com
   • solnic.eu
   • github.com/solnic
   • @_solnic_
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3. 4 Facts about This Talk
   • It has 2 sections: “ActiveRecord
   Retrospective” and “DataMapper 2”
   • It has 2 obligatory pictures of a cat
   • It has only 1 quote from Martin
   Fowler’s PoEAA book
   • It has only 16 code examples
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4. ActiveRecord
   Retrospective
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5. ActiveRecord
   Pattern Facts
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6. Active Record Pattern Facts
   • Simple ORM Pattern
   • Designed for simple usecases where the
   business domain is simple. ie. basic
   CRUD
   • Mixes together data & behavior
   • 1:1 mapping between database schema &
   objects (means tight coupling with the
   db)
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7. ActiveRecord
   in Rails
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8. class User < ActiveRecord::Base
   end
   Active Record in Rails
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9. Active Record in Rails
   (User.methods.sort - Object.methods.sort).count
   # => 391
   391
   new public class methods...
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10. WHAT??!! I’m perfectly fine!!!
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11. • Persistence
    • Validations
    • Associations
    • Life cycle hooks
    • Typecasting
    • Mass-assignment security
    • ...and much much more!
    Active Record
    retrospective
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12. Active Record
    retrospective
    • Slow test suites
    • Lack of real unit tests
    • God objects
    • Code hard to reuse and extend
    • Code hard to refactor
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13. I don’t think I can take it Anymore!
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14. I don’t care if
    we can create a
    blog in 15
    minutes
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15. but I do care if
    we can work on a
    project for 15
    months and keep
    it in a good
    shape
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16. DataMapper 2
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17. DataMapper 2
    “A layer of Mappers that moves data between
    objects and a database while keeping them
    independent of each other and the mapper itself.”
    Martin Fowler
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18. DataMapper 2
    Repository
    Mapper & Session
    Domain Model
    Validation Serialization Extensions
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19. Domain Model
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20. Domain Model
    class City
    attr_reader :name, :lat, :lng
    def initialize(attributes)
    @name, @lat, @lng = attributes.values_at(
    :name, :lat, :lng
    )
    end
    end
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21. Domain Model
    class CityMapper < DataMapper::Mapper
    map :name, :lat, :lng
    end
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22. Domain Model
    city = City.new(
    name: 'Kraków',
    lat: 123456.789,
    lng: 987654.321
    )
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23. Domain Model
    class GeoLocation
    include Virtus::ValueObject
    attribute :lat, Float
    attribute :lng, Float
    end
    class City
    include Virtus
    attribute :name, String
    attribute :location, GeoLocation
    end
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24. Domain Model
    class CityMapper < DataMapper::Mapper
    map :name
    map :location, to: [ :lat, :lng ]
    end
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25. Session
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26. Session
    class Person
    include Virtus
    attribute :name, String
    attribute :city, City
    end
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27. Session
    class PersonMapper < DataMapper::Mapper
    map :name
    has 1, :city
    end
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28. Session
    city = City.new(
    name: 'Kraków',
    location: {
    lat: 123456789.123,
    lng: 987654321.987
    }
    )
    person = Person.new(name: 'Piotr')
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29. Session
    DataMapper.session do |session|
    session.track(city)
    session.track(person)
    person.city = city
    session.insert(person)
    session.commit
    end
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30. Repository
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31. Repository
    Repository
    Relation
    Optimizer
    Datastore Adapter
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32. Repository
    • 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
    • Designed to support per database
    optimizations
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33. Repository
    relation = Veritas::Relation.new([
    [ :id, Integer ], [ :name, String ], [ :color, String ] ],
    [
    [ 1, 'Nut', 'Red' ],
    [ 2, 'Bolt', 'Green' ],
    [ 3, 'Screw', 'Blue' ],
    [ 4, 'Screw', 'Red' ],
    [ 5, 'Cam', 'Blue' ],
    [ 6, 'Cog', 'Red' ],
    ]
    )
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34. Repository
    # projection
    new_relation = relation.project([ :id ])
    # removal
    new_relation = relation.remove([ :name ])
    # rename
    new_relation = relation.rename(id: :other_id,
    name: :other_name)
    # restriction
    new_relation = relation.restrict { |r|
    r.color.eq('Red').or(r.color.eq('Blue'))
    }
    # natural join
    new_relation = relation.join(other)
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35. Repository
    include Veritas
    adapter = Adapter::DataObjects.new(
    "postgres://localhost/test")
    header = [ [ :id, Integer ], [ :name,
    String ], [ :color, String ] ]
    relation = Relation::Base.new(
    'items', header)
    gateway = Relation::Gateway.new(
    adapter, relation)
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36. Repository
    new_relation = gateway.restrict { |r|
    r.color.eq('Red').or(r.color.eq('Blue'))
    }
    new_relation.to_a
    # SELECT "id", "name", "color"
    # FROM items
    # WHERE (
    # "color" = 'Red' OR "color" = 'Blue'
    # )
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37. What’s Done
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38. What’s Done
    • Veritas
    • Veritas DataObject Adapter for PostgreSQL
    • Veritas Optimizer
    • Virtus (Domain Model features)
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39. Work in Progress
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40. Work in Progress
    • “write” support for Veritas
    • Mapper
    • Session/Unit of Work
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41. Work in Progress
    • Validations
    • Migrations
    • Constraints
    • Extension Interfaces
    • More Veritas adapters (sqlite, MySQL,
    MongoDB, Riak etc.)
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42. Development
    Process
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43. Development Process
    • All “levels” of API are treated with the
    same amount of care & love
    • Using metric tools to verify code quality
    • Mutation testing with Heckle
    • 100% YARD documentation coverage
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44. Virtus Project
    on CodeClimate
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45. Resources
    • https://github.com/datamapper/dm-
    core/wiki/Roadmap
    • https://github.com/dkubb/veritas
    • https://github.com/dkubb/veritas-do-
    adapter
    • https://github.com/solnic/virtus
    • https://github.com/solnic/dm-mapper
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46. THANKS!
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