Open Source Ecosystems

= dm-is-self_referential

A datamapper[http://github.com/datamapper/dm-core] plugin that allows declarative specification of self referential m:m relationships.

== Examples

class User

include DataMapper::Resource

property :id, Serial
property :name, String, :nullable => false, :unique => true, :unique_index => true

# with default options
#
# will define and thus be able to automigrate the UserToUser model
# with the following relationships established between the participating models
#
#   has n, :user_children, 'UserToUser', :child_key => [ :source_id ]
#   has n, :user_parents,  'UserToUser', :child_key => [ :target_id ]
#
# once dm-core has full support for the following m:m relationships built in,
# these will also get established.
#
#   has n, :children, self, :through => :user_children, :via => :target
#   has n, :parents , self, :through => :user_parents,  :via => :source
#
# In the meantime, the following helper methods get defined
#
#   def children
#     children_ids = self.user_children.map { |r| r.target_id }
#     self.class.all(:id => children_ids)
#   end
#
#   def parents
#     parent_ids = self.user_parents.map { |r| r.source_id }
#     self.class.all(:id => parent_ids)
#   end
#
is :self_referential


# With explicit intermediate model name and default options
#
# Will define and thus be able to automigrate the Friendship model
# with the following relationships established between the participating models
#
#   has n, :user_children, 'Friendship', :child_key => [ :source_id ]
#   has n, :user_parents,  'Friendship', :child_key => [ :target_id ]
#
# Once dm-core has full support for the following m:m relationships built in,
# these will also get established.
#
#   has n, :children, self, :through => :user_children, :via => :target
#   has n, :parents , self, :through => :user_parents,  :via => :source
#
# In the meantime, the following helper methods get defined
#
#   def children
#     children_ids = self.user_children.map { |r| r.target_id }
#     self.class.all(:id => children_ids)
#   end
#
#   def parents
#     parent_ids = self.user_parents.map { |r| r.source_id }
#     self.class.all(:id => parent_ids)
#   end
#
is :self_referential, :through => 'Friendship'


# With explicit intermediate model name and customized options
#
# Will define and thus be able to automigrate the UserRelationship model
# with the following relationships established between the participating models
#
#   has n, :user_children, 'UserRelationship', :child_key => [ :parent_user_id ]
#   has n, :user_parents,  'UserRelationship', :child_key => [ :child_user_id  ]
#
# Once dm-core has full support for the following m:m relationships built in,
# these will also get established.
#
#   has n, :child_users,  User, :through => :user_children, :via => :child_user
#   has n, :parent_users, User, :through => :user_parents,  :via => :parent_user
#
# In the meantime, the following helper methods get defined
#
#   def child_users
#     children_ids = self.user_children.map { |r| r.target_id }
#     self.class.all(:id => children_ids)
#   end
#
#   def parent_users
#     parent_ids = self.user_parents.map { |r| r.source_id }
#     self.class.all(:id => parent_ids)
#   end
#
is :self_referential, :through => 'UserRelationship',
  :children => :child_users,
  :parents  => :parent_users,
  :source   => :parent_user,
  :target   => :child_user