adding initial support for belongs_to associations

lib/couchrest/extended_document.rb

@@ -19,6 +19,7 @@ module CouchRest
     include CouchRest::Mixins::Collection
     include CouchRest::Mixins::AttributeProtection
     include CouchRest::Mixins::Attributes
+    include CouchRest::Mixins::Associations
 
     # Including validation here does not work due to the way inheritance is handled.
     #include CouchRest::Validation

lib/couchrest/mixins.rb

@@ -10,3 +10,4 @@ require File.join(mixins_dir, 'class_proxy')
 require File.join(mixins_dir, 'collection')
 require File.join(mixins_dir, 'attribute_protection')
 require File.join(mixins_dir, 'attributes')
+require File.join(mixins_dir, 'associations')

lib/couchrest/mixins/associations.rb

@@ -0,0 +1,58 @@
+module CouchRest
+  module Mixins
+    module Associations
+
+      # Basic support for relationships between ExtendedDocuments
+      
+      def self.included(base)
+        base.extend(ClassMethods)
+      end
+
+      module ClassMethods
+
+        def belongs_to(attrib, *options)
+          opts = {
+            :foreign_key => attrib.to_s + '_id',
+            :class_name => attrib.to_s.camelcase
+          }
+          case options.first
+          when Hash
+            opts.merge!(options.first)
+          end
+
+          begin
+            opts[:class] = opts[:class_name].constantize
+          rescue
+            raise "Unable to convert belongs_to class name into Constant for #{self.name}##{attrib}"
+          end
+
+          prop = property(opts[:foreign_key])
+
+          create_belongs_to_getter(attrib, prop, opts)
+          create_belongs_to_setter(attrib, prop, opts)
+
+          prop
+        end
+
+        def create_belongs_to_getter(attrib, property, options)
+          class_eval <<-EOS, __FILE__, __LINE__ + 1
+            def #{attrib}
+              @#{attrib} ||= #{options[:class_name]}.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)
+              @#{attrib} = value
+              self.#{options[:foreign_key]} = value.nil? ? nil : value.id
+            end
+          EOS
+        end
+
+      end
+
+    end
+  end
+end