DataMapper as an Alternative to ActiveRecord

DataMapper als
Alternative zu
ActiveRecord ?
Rails-Konferenz.de 2009
Hussein Morsy & Tanja Otto

1

SalesLentz::DevTeam

2

Über uns

# internes Entwicklerteam von Sales-Lentz
# IBEs für Reisen, Bustickets, Eventtickets
# seit 2006 entwickeln wir mit Ruby on Rails
# Buch Ruby on Rails 2 Galileo Press
# http://railsbuch.de
# http://twitter.com/ajnato
# http://twitter.com/HusseinMorsy

3

Wer ist ein Rails Newbie ?

4

Dan Kubb – Ruby Hero

5

Wer setzt DataMapper ein ?

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ActiveRecord Intro
require 'rubygems'
require 'active_record'

ActiveRecord::Base.establish_connection(:adapter => "sqlite3",
:database => "db/shop.sqlite3")

# Tabelle manuell oder per Migration erstellen

# CREATE TABLE shoes (
# ...
# );

class Shoe < ActiveRecord::Base
end

Shoe.create(:brand => "Geox", :price => 52.5)

puts Shoe.first.brand
# => Geox

8

DataMapper Intro
require 'rubygems'
require 'dm-core'
DataMapper.setup(:default, "sqlite3://db/shop.sqlite3")

class Shoe
include DataMapper::Resource

property :id, Serial
property :brand, String
property :price, Float
property :available, Boolean
end

Shoe.auto_migrate!

Shoe.create(:brand => "Geox", :price => 52.5)

puts Shoe.first.brand
# => Geox

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ActiveRecord Migrations
# Neue Tabelle erstellen

class CreateShoes < ActiveRecord::Migration
def self.up
create_table :shoes do |t|
t.string :brand
t.float :price

t.timestamps
end
end

def self.down
drop_table :shoes
end
end

rake db:migrate

11

ActiveRecord Migrations
# Neues Feld hinzufügen

class AddAvailableToShoes < ActiveRecord::Migration
def self.up
add_column :shoes, :available, :boolean
end

def self.down
remove_column :shoes, :available
end
end

rake db:migrate

12

DataMapper Migrations

class Shoe

end

# Tabelle shoes erstellen
# Vorsicht: Daten gehen verloren
Shoe.auto_migrate!

# alle Tabellen erstellen
DataMapper.auto_migrate!

# In Datamapper gibt es auch Migrations, ähnlich wie in ActiveRecord
# siehe dm-migrations

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DataMapper Migrations
# Neues Feld hinzufügen

class Shoe

end

Shoe.auto_migrate!

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DataMapper Extended Types
require 'rubygems'
require 'dm-core'
# erweiterte Datentypen
require 'dm-types'
class Shoe
# primitive Datentypen
# ...
# erweiterte Datentypen
property :color, Enum[:red, :green, :blue]
property :image_path, FilePath
end

shoe = Shoe.new
shoe.color = :red
shoe.image_path = "/images/shoes.jpg"
shoe.image_path.class
# => Pathname
shoe.image_path.basename
# => shoes.jpg

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ActiveRecord Extended Types

?
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ActiveRecord Defaults

def self.up
t.string :brand
t.float :price
t.float :tax, :default => 19.0

t.timestamps
end
end

def self.down
drop_table :shoes
end
end

rake db:migrate

19

DataMapper Defaults
# Dynamische Default-Werte

class Shoe

property :tax, Float, :default => 19.0
end


my_shoe = Shoe.create(:brand => "demo", :price => 99.9)
puts my_shoe.tax
# => 19.0

20

DataMapper Dynamic Defaults
# Dynamische Default-Werte

class Shoe

property :tax, Float, :default => 19
property :sale, Float, :default =>
Proc.new { |r, p| r.price * 0.5 }
end


puts my_shoe.sale
# => 49.95

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ActiveRecord Dynamic Defaults

?
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ActiveRecord Validations
# Model ohne Validierung

class Woman < ActiveRecord::Base
end

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ActiveRecord Validations
# Model mit Validierung

validates_presence_of :name
validates_length_of :title, :within => 2..20
validates_format_of :email,
:with => /^([^@s]+)@((?:[-a-z0-9]+.)+[a-z]{2,})$/i
validates_uniqueness_of :email
end

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DataMapper Validations
# Model ohne Validierung

class Woman

property :name, String
property :title, String
property :email, String

end

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DataMapper Validations
# Model mit Validierung

class Woman

property :name, String, :nullable => false
property :title, String, :length => 2..20
property :email, String, :nullable => false,
:format => :email_address,
:unique => true

end

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ActiveRecord Identity Map
Shoe.first.eql? Shoe.first

# => false

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DataMapper Identity Map
Shoe.first.eql? Shoe.first

# => true

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DataMapper Lazy Loading
class Shoe

property :short_description, String, :length => 255, :lazy => true
property :description, Text # default :lazy => true
end

# SELECT id, brand, price from shoes where id=1
my_shoe = Shoe.get(1)

# SELECT short_description from shoes where id=1
my_shoe.short_description

# SELECT description from shoes where id=1
my_shoe.description

32

DataMapper Lazy Loading
class Shoe

property :short_description, String, :length => 255, :lazy => [:details]
property :description, Text, :lazy => [:details]
end

# SELECT id, brand, price from shoes where id=1
my_shoe = Shoe.get(1)

# SELECT short_description,description from shoes where id=1
my_shoe.short_description

# Keine Datenbankabfrage
my_shoe.description

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ActiveRecord Lazy Loading

?
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ActiveRecord Lazy Loading
end

my_shoe = Shoe.all(:select => "id, brand, price").first
puts my_shoe.brand

my_shoe.description
# => Exception

puts Shoe.first(:select => "id,description")

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ActiveRecord Keys
# Primary Keys automatisch in Migration
# Immer Integer

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DataMapper Keys
class Woman

property :id, Integer, :serial => true
# ...
end

Woman.get(7)

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DataMapper Keys
# Kurzform

class Woman

# ...
end

Woman.get(7)

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DataMapper Keys
# Natürlicher Key

class Woman

property :steuer_identifikationsnummer, :key => true
end

Woman.get("i2930d980324")

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DataMapper Keys
# Composite Keys

class Woman

property :steuer_identifikationsnummer, :key => true
property :pass_nr, :key => true
end

Woman.get("i2930d980324","949823902-X-234s")

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ActiveRecord Search
end

# the ActiveRecord-SQL-Style
Shoe.find(:all, :conditions => ["brand=? AND price < ?", "Geox", 130.0])

# brand = Geox
Shoe.all(:conditions => {:brand => "Geox"})

# brand != Geox
Shoe.all(:conditions => ["brand IS NOT ?", "Geox"])

# brand IS NOT NULL
Shoe.all(:conditions => "brand IS NOT NULL")

# brand like "G%"
Shoe.all(:conditions => "brand LIKE G%")

# brand = "Geox" OR brand= "Converse"
Shoe.all(:conditions => {:brand => ["Geox", "Converse"]})

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DataMapper Search
class Shoe

end


Shoe.all(:conditions => ["brand=? AND price < ?", "Geox", 130.0])

44

DataMapper Search
Shoe.all(:conditions => ["brand=? AND price < ?", "Geox", 130.0])

# the DataMapper-Style
Shoe.all(:brand => "Geox", :price.lt => 130.0)

# brand != Geox
Shoe.all(:brand.not => "Geox")

# brand IS NOT NULL
Shoe.all(:brand.not => nil)

# brand like "G%"
Shoe.all(:brand.like => "G%")

# price <= 60.0
Shoe.all(:price.lte => 60.0)

# brand = "Geox" OR brand= "Converse"
Shoe.all(:brand => ["Geox", "Converse"])

45

ActiveRecord Named Scope
named_scope :available, :conditions => ['available = ?', true]
named_scope :cheaper,
lambda { |max_price| { :conditions => ['price < ?', max_price] } }
end

Shoe.available.cheaper(20)

47

DataMapper Named Scope
class Shoe


def self.available
all(:available => true)
end

def self.cheaper(max_price)
all(:price.lt => max_price)
end
end

Shoe.available.cheaper(210.0)

48

ActiveRecord Associations
class Woman
has_many :shoes
end

class Shoe
belongs_to :woman
has_many :categories, :through => :categorisations
end

50

DataMapper Associations
class Woman
has n, :shoes
end

class Shoe
property :woman_id, Integer

belongs_to :woman
has n,:categories, :through => :categorisations
end

51

ActiveRecord Timestamps
# Neue Tabelle erstellen mit einer Migration
def self.up
t.string :brand
t.float :price

t.timestamps
end
end

def self.down
drop_table :shoes
end
end

# Model
end

puts my_shoe.created_at
puts my_shoe.updated_at

53

DataMapper Timestamps
require 'initdb'

class Shoe

property :created_at, DateTime
property :updated_at, DateTime
end


# => nil

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require 'initdb'
require 'dm-timestamps'

class Shoe

property :created_at, DateTime
property :updated_at, DateTime
end


my_shoe = Shoe.create(:title => "demo", :price => 99.9)
# => 2009-08-30T04:29:36+00:00

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require 'initdb'

class Shoe


timestamps :created_at, :updated_at
end


# => 2009-08-30T04:29:36+00:00

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require 'initdb'

class Shoe


timestamps :at
end


# => 2009-08-30T04:29:36+00:00

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ActiveRecord Multi Databases

?
59

DataMapper Multi Databases
DataMapper.setup(:default, "sqlite3:///#{Dir.pwd}/db/crm.sqlite3")
DataMapper.setup(:shop, "sqlite3:///#{Dir.pwd}/db/shop.sqlite3")

class Woman
end

class Shoe
def self.default_repository_name
:shop
end


end

60

Naming Conventions

61

ActiveRecord Naming Conventions
set_table_name "tbl_Shoe"
end

set_table_name "tbl_Woman"
end

62

DataMapper Naming Conventions
class Shoe
storage_names[:default] = 'tbl_Shoe'
#....
end

class Woman
storage_names[:default] = 'tbl_Woman'
#....
end

63

DataMapper Naming Conventions
repository(:default).adapter.resource_naming_convention =
lambda { |klass| "tbl_#{klass.camel_case}" }

class Shoe
# ....
end

class Woman
#....
end

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Legacy Databases

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ActiveRecord Legacy Databases

?
66

DataMapper Legacy Databases
class Woman
storage_names[:default] = 'tbl_woman'

property :id, String, :field => "NR", :key => true
property :firstname, String, :field => "VORNAME"
property :title, String, :field => "ANREDE"
property :email, String, :nullable => false,
:format => :email_address, :unique => true
end

# Im Gegensatz zu ActiveRecord werden nur die angegebenen Felder gelesen

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ActiveRecord Adapter

MySQL

PostgreSQL

SQLite

Oracle

69

DataMapper Adapter

MySQL YAML IMAP ...

PostgreSQL

SQLite

Oracle

70

one more thing...

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Solo Division Winner: Jacques Crocker

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mit DataMapper gemacht!

76

http://github.com/merbjedi/alertme_tv

77

DataMapper as an Alternative to ActiveRecord

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