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