= 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