couchrest_model/lib/couchrest/model/associations.rb

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module CouchRest
module Model
module Associations
# Basic support for relationships between ExtendedDocuments
def self.included(base)
base.extend(ClassMethods)
end
module ClassMethods
# Define an association that this object belongs to.
#
def belongs_to(attrib, *options)
opts = {
:foreign_key => attrib.to_s + '_id',
:class_name => attrib.to_s.camelcase,
:proxy => nil
}
case options.first
when Hash
opts.merge!(options.first)
end
begin
opts[:class] = opts[:class_name].constantize
rescue
raise "Unable to convert class name into Constant for #{self.name}##{attrib}"
end
prop = property(opts[:foreign_key], opts)
create_belongs_to_getter(attrib, prop, opts)
create_belongs_to_setter(attrib, prop, opts)
prop
end
# Provide access to a collection of objects where the associated
# property contains a list of the collection item ids.
#
# The following:
#
# collection_of :groups
#
# creates a pseudo property called "groups" which allows access
# to a CollectionOfProxy object. Adding, replacing or removing entries in this
# proxy will cause the matching property array, in this case "group_ids", to
# be kept in sync.
#
# Any manual changes made to the collection ids property (group_ids), unless replaced, will require
# a reload of the CollectionOfProxy for the two sets of data to be in sync:
#
# group_ids = ['123']
# groups == [Group.get('123')]
# group_ids << '321'
# groups == [Group.get('123')]
# groups(true) == [Group.get('123'), Group.get('321')]
#
# Of course, saving the parent record will store the collection ids as they are
# found.
#
# The CollectionOfProxy supports the following array functions, anything else will cause
# a mismatch between the collection objects and collection ids:
#
# groups << obj
# groups.push obj
# groups.unshift obj
# groups[0] = obj
# groups.pop == obj
# groups.shift == obj
#
# Addtional options match those of the the belongs_to method.
#
# NOTE: This method is *not* recommended for large collections or collections that change
# frequently! Use with prudence.
#
def collection_of(attrib, *options)
opts = {
:foreign_key => attrib.to_s.singularize + '_ids',
:class_name => attrib.to_s.singularize.camelcase,
:proxy => nil
}
case options.first
when Hash
opts.merge!(options.first)
end
begin
opts[:class] = opts[:class_name].constantize
rescue
raise "Unable to convert class name into Constant for #{self.name}##{attrib}"
end
opts[:readonly] = true
prop = property(opts[:foreign_key], [], opts)
create_collection_of_property_setter(attrib, prop, opts)
create_collection_of_getter(attrib, prop, opts)
create_collection_of_setter(attrib, prop, opts)
prop
end
private
def create_belongs_to_getter(attrib, property, options)
base = options[:proxy] || options[:class_name]
class_eval <<-EOS, __FILE__, __LINE__ + 1
def #{attrib}
@#{attrib} ||= #{options[:foreign_key]}.nil? ? nil : #{base}.get(self.#{options[:foreign_key]})
end
EOS
end
def create_belongs_to_setter(attrib, property, options)
class_eval <<-EOS, __FILE__, __LINE__ + 1
def #{attrib}=(value)
self.#{options[:foreign_key]} = value.nil? ? nil : value.id
@#{attrib} = value
end
EOS
end
### collection_of support methods
def create_collection_of_property_setter(attrib, property, options)
# ensure CollectionOfProxy is nil, ready to be reloaded on request
class_eval <<-EOS, __FILE__, __LINE__ + 1
def #{options[:foreign_key]}=(value)
@#{attrib} = nil
write_attribute("#{options[:foreign_key]}", value)
end
EOS
end
def create_collection_of_getter(attrib, property, options)
base = options[:proxy] || options[:class_name]
class_eval <<-EOS, __FILE__, __LINE__ + 1
def #{attrib}(reload = false)
return @#{attrib} unless @#{attrib}.nil? or reload
ary = self.#{options[:foreign_key]}.collect{|i| #{base}.get(i)}
@#{attrib} = ::CouchRest::CollectionOfProxy.new(ary, self, '#{options[:foreign_key]}')
end
EOS
end
def create_collection_of_setter(attrib, property, options)
class_eval <<-EOS, __FILE__, __LINE__ + 1
def #{attrib}=(value)
@#{attrib} = ::CouchRest::CollectionOfProxy.new(value, self, '#{options[:foreign_key]}')
end
EOS
end
end
end
end
# Special proxy for a collection of items so that adding and removing
# to the list automatically updates the associated property.
class CollectionOfProxy < Array
attr_accessor :property
attr_accessor :casted_by
def initialize(array, casted_by, property)
self.property = property
self.casted_by = casted_by
(array ||= []).compact!
casted_by[property.to_s] = [] # replace the original array!
array.compact.each do |obj|
casted_by[property.to_s] << obj.id
end
super(array)
end
def << obj
casted_by[property.to_s] << obj.id
super(obj)
end
def push(obj)
casted_by[property.to_s].push obj.id
super(obj)
end
def unshift(obj)
casted_by[property.to_s].unshift obj.id
super(obj)
end
def []= index, obj
casted_by[property.to_s][index] = obj.id
super(index, obj)
end
def pop
casted_by[property.to_s].pop
super
end
def shift
casted_by[property.to_s].shift
super
end
end
end