README.rdoc

dm-is-remixable¶ ↑

DataMapper::Is::Remixable allows you to create re-usable chunks of relational data, its kind of like multiple inheritance for models.

For example:

# Comments are everywhere, why define them over and over?:
module Comment
  include DataMapper::Resource
  is :remixable

  property :id,         Serial
  property :body,       String
  property :created_at, DateTime
end

# Lots of things can be addressable; people, buildings
module Addressable
  include DataMapper::Resource

  is :remixable,
    :suffix => "address" #Default suffix is module name pluralized

  property :id,         Serial

  property :label,      String #home, work, etc...

  property :address1,   String, :length => 255
  property :address2,   String, :length => 255

  property :city,       String, :length => 128
  property :state,      String, :length => 2
  property :zip,        String, :length => 5..10
end

module Vote
  include DataMapper::Resource

  is :remixable

  property :id,         Serial
  property :opinion,    Enum["good","bad"]
end

class Location
  include DataMapper::Resource

  #Location can have 1 address
  remix 1, :addressables

  # This does the following:
  # - creates a class called LocationAddress
      (default name would be LocationAddressable, but Addressable#suffix was specified)
  # - duplicates the properties of Addressable within LocationAddress
  # - a table called location_addresses
  # - creates Location#location_addresses accessor

  #... methods, properties, etc ...#
end

class User
  include DataMapper::Resource

  #User can have many addresses
  remix n, :addressables, :as => "addresses"
  # - creates a class called UserAddress
      (default name would be UserAddressable, but Addressable#suffix was specified)
  # - duplicates the properties of Addressable within UserAddress
  # - a table called user_addresses
  # - creates User#user_addresses accessor
  # - creates an accessor alias User#addresses

  enhance :addressables do
    storage_names[:default] = "a_different_table_name"
    property :label, Enum["work","home"]

    #This adds a column to user_addresses to store an address label
  end

  #... methods, properties, etc ...#
end

class Article
  include DataMapper::Resource

  remix n, :comments, :for => "User"
  # - creates a class called ArticleComment
  # - duplicates the properties of Comment within ArticleComment
  # - a table called article_comments
  # - creates Article#article_comments
  # - creates User#article_comments

  #... methods, properties, etc ...#

end

class Video
  include DataMapper::Resource

  remix n, :comments, :for => "User", :as => "comments"
  # - creates a class called VideoComment
  # - duplicates the properties of Comment within VideoComment
  # - a table called video_comments
  # - creates Video#video_comments
  # - creates User#video_comments
  # - create Video#comments

  enhance :comments do
    # VideoComment now has the method #reverse
    def reverse
      return self.body.reverse
    end

    #I like YouTubes ability for users to vote comments up and down
    remix 1, :votes, :for => "User"
    # - creates a class called VideoCommentVote
    # - duplicates the properties of Vote within VideoCommentVote
    # - a table called video_comment_votes
    # - creates Video#video_comments#votes

  end

  #... methods, properties, etc ...#
end

Further, remixables can namespace methods that should exist in the generated and remixing classes, if these modules are present the are attached appropriately to the other classes.

module ExampleRemixable
  include DataMapper::Resource
  is :remixable

  #... your properies ...

  # Class methods that will be attached to class doing the remixing...
  #
  # These methods would be attached to the User class given:
  #   User.remixes n, :images
  #
  module RemixerClassMethods
  end

  # Instances methods that will be attached to objects of the class doing the remixing...
  #
  # These methods would be attached to User objects given:
  #   User.remixes n, :images
  #
  module RemixerInstanceMethods
  end

  # Class methods that will be attached to genereated remixed class
  #
  # These methods would be attached to the UserImage class given:
  #   User.remixes n, :images
  #
  module RemixeeClassMethods
  end

  # Instances methods that will be attached to objects of the genereated remixed class
  #
  # These methods would be attached to UserImage objects given:
  #   User.remixes n, :images
  #
  module RemixeeInstanceMethods
  end
end