couchrest_model/lib/couchrest/model/associations.rb

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module CouchRest
module Model
module Associations
# Basic support for relationships between CouchRest::Model::Base
def self.included(base)
base.extend(ClassMethods)
end
module ClassMethods
# Define an association that this object belongs to.
#
# An attribute will be created matching the name of the attribute
# with '_id' on the end, or the foreign key (:foreign_key) provided.
#
# Searching for the assocated object is performed using a string
# (:proxy) to be evaulated in the context of the owner. Typically
# this will be set to the class name (:class_name), or determined
# automatically if the owner belongs to a proxy object.
#
# If the association owner is proxied by another model, than an attempt will
# be made to automatically determine the correct place to request
# the documents. Typically, this is a method with the pluralized name of the
# association inside owner's owner, or proxy.
#
# For example, imagine a company acts as a proxy for invoices and clients.
# If an invoice belongs to a client, the invoice will need to access the
# list of clients via the proxy. So a request to search for the associated
# client from an invoice would look like:
#
# self.company.clients
#
# If the name of the collection proxy is not the pluralized assocation name,
# it can be set with the :proxy_name option.
#
def belongs_to(attrib, *options)
opts = merge_belongs_to_association_options(attrib, options.first)
property(opts[:foreign_key], opts)
create_belongs_to_getter(attrib, opts)
create_belongs_to_setter(attrib, opts)
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 = merge_belongs_to_association_options(attrib, options.first)
opts[:foreign_key] = opts[:foreign_key].pluralize
opts[:readonly] = true
property(opts[:foreign_key], [], opts)
create_collection_of_property_setter(attrib, opts)
create_collection_of_getter(attrib, opts)
create_collection_of_setter(attrib, opts)
end
private
def merge_belongs_to_association_options(attrib, options = nil)
opts = {
:foreign_key => attrib.to_s.singularize + '_id',
:class_name => attrib.to_s.singularize.camelcase,
:proxy_name => attrib.to_s.pluralize
}
opts.merge!(options) if options.is_a?(Hash)
# Generate a string for the proxy method call
# Assumes that the proxy_owner_method from "proxyable" is available.
if opts[:proxy].to_s.empty?
opts[:proxy] = if proxy_owner_method
"self.#{proxy_owner_method}.#{opts[:proxy_name]}"
else
opts[:class_name]
end
end
opts
end
def create_belongs_to_getter(attrib, options)
class_eval <<-EOS, __FILE__, __LINE__ + 1
def #{attrib}
@#{attrib} ||= #{options[:foreign_key]}.nil? ? nil : #{options[:proxy]}.get(self.#{options[:foreign_key]})
end
EOS
end
def create_belongs_to_setter(attrib, 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, 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, options)
class_eval <<-EOS, __FILE__, __LINE__ + 1
def #{attrib}(reload = false)
return @#{attrib} unless @#{attrib}.nil? or reload
ary = self.#{options[:foreign_key]}.collect{|i| #{options[:proxy]}.get(i)}
@#{attrib} = ::CouchRest::CollectionOfProxy.new(ary, self, '#{options[:foreign_key]}')
end
EOS
end
def create_collection_of_setter(attrib, 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|
check_obj(obj)
casted_by[property.to_s] << obj.id
end
super(array)
end
def << obj
check_obj(obj)
casted_by[property.to_s] << obj.id
super(obj)
end
def push(obj)
check_obj(obj)
casted_by[property.to_s].push obj.id
super(obj)
end
def unshift(obj)
check_obj(obj)
casted_by[property.to_s].unshift obj.id
super(obj)
end
def []= index, obj
check_obj(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
protected
def check_obj(obj)
raise "Object cannot be added to #{casted_by.class.to_s}##{property.to_s} collection unless saved" if obj.new?
end
end
end