Payload map

lib/payload_map.rb

@@ -0,0 +1,44 @@
+module SData  
+  module PayloadMap
+    def define_payload_map(map)
+      cattr_accessor :payload_map
+      cattr_accessor :payload
+
+      self.payload_map = map
+      self.payload = payload_fields_proxy
+    end
+
+  protected
+
+    module PayloadFieldsProxy
+      module ClassMethods
+        def define_readers(readers)
+          readers.each { |reader| attr_reader reader }
+        end
+      end
+
+      module InstanceMethods
+        def set_values(values)
+          values.each_pair do |key, value|
+            ivar_sym = "@#{key.to_s}".to_sym
+            instance_variable_set ivar_sym, value
+          end
+        end
+      end
+    end
+
+    def payload_fields_proxy
+      proxy_class = Class.new
+      proxy_class.extend PayloadFieldsProxy::ClassMethods
+      proxy_class.__send__ :include, PayloadFieldsProxy::InstanceMethods
+      proxy_class.define_readers(self.payload_map.keys)
+
+      returning proxy_class.new do |proxy|
+        field_values = self.payload_map.merge(self.payload_map) { |key, value| value[:static_value] }
+        proxy.set_values(field_values)
+      end
+    end
+  end
+end
+
+VirtualBase.extend SData::PayloadMap

test/unit/payload_map_spec.rb

@@ -0,0 +1,37 @@
+require File.join(File.dirname(__FILE__), 'spec_helper')
+
+describe SData::PayloadMap do
+  context "given a VirtualBase class extended by SData::PayloadMap" do
+    before :all do
+      VirtualBase.extend SData::PayloadMap
+    end
+
+    it "should respond to #payload_map class method" do
+      VirtualBase.should respond_to(:define_payload_map)
+    end
+
+    describe "#define_payload_map" do
+      context "when mapping leads to static value" do
+        before :all do
+          VirtualBase.define_payload_map :tax_reference => { :static_value => 'Some static tax reference' }
+        end
+
+        subject { VirtualBase.new(Object) }
+
+        it { should respond_to(:payload) }
+
+        context "when correspondent field method is called" do
+          it "should return given static value" do
+            subject.payload.tax_reference.should == 'Some static tax reference'
+          end
+        end
+
+        describe "#payload_map" do
+          subject { VirtualBase.new(Object).payload_map }
+
+          it { should == { :tax_reference => { :static_value => 'Some static tax reference' } } }
+        end
+      end
+    end
+  end
+end