Updated code to use Property#instance_variable_name when possible

* Removed unecessary String#ensure_starts_with and
  String#ensure_ends_with

lib/data_mapper/adapters/data_objects_adapter.rb

@@ -69,7 +69,7 @@ def create_with_returning?
       # Methods dealing with a single instance object
       def create(repository, instance)
         properties = instance.dirty_attributes
-        values = properties.map { |property| instance.instance_variable_get(property.name.to_s.ensure_starts_with('@')) }
+        values = properties.map { |property| instance.instance_variable_get(property.instance_variable_name) }
 
         sql = send(create_with_returning? ? :create_statement_with_returning : :create_statement, instance.class, properties)
 
@@ -117,7 +117,7 @@ def read(repository, resource, key)
 
       def update(repository, instance)
         properties = instance.dirty_attributes
-        values = properties.map { |property| instance.instance_variable_get(property.name.to_s.ensure_starts_with('@')) }
+        values = properties.map { |property| instance.instance_variable_get(property.instance_variable_name) }
 
         sql = update_statement(instance.class, properties)
         parameters = (values + instance.key)
@@ -138,7 +138,7 @@ def delete(repository, instance)
         connection = create_connection
         command = connection.create_command(delete_statement(instance.class))
 
-        key = instance.class.key(name).map { |property| instance.instance_variable_get(property.name.to_s.ensure_starts_with('@')) }
+        key = instance.class.key(name).map { |property| instance.instance_variable_get(property.instance_variable_name) }
         affected_rows = command.execute_non_query(*key).to_i
 
         close_connection(connection)

lib/data_mapper/property.rb

@@ -225,7 +225,7 @@ def initialize(target, name, type, options)
 
       @instance_variable_name = "@#{@name}"
 
-      @getter = @type.is_a?(TrueClass) ? @name.to_s.ensure_ends_with('?').to_sym : @name
+      @getter = @type.is_a?(TrueClass) ? "#{@name}?".to_sym : @name
 
 
       # if it has a lazy key it is lazy. :lazy is now an array of contexts not bool
@@ -280,7 +280,7 @@ def #{name}
       if type == TrueClass
         @target.class_eval <<-EOS, __FILE__, __LINE__
           #{reader_visibility}
-          alias #{name.to_s.ensure_ends_with('?')} #{name}
+          alias #{name}? #{name}
         EOS
       end
     rescue SyntaxError

lib/data_mapper/resource.rb

@@ -37,10 +37,10 @@ def self.dependencies
     attr_accessor :loaded_set
 
     def [](name)
-      ivar_name = "@#{name}"
       property  = self.class.properties(repository.name)[name]
+      ivar_name = property.instance_variable_name
 
-      unless new_record? || attribute_loaded?(name)
+      unless new_record? || instance_variable_defined?(ivar_name)
         lazy_load(name)
       end
 
@@ -49,8 +49,8 @@ def [](name)
     end
 
     def []=(name, value)
-      ivar_name = "@#{name}"
       property  = self.class.properties(repository.name)[name]
+      ivar_name = property.instance_variable_name
 
       if property && property.lock?
         instance_variable_set("@shadow_#{name}", instance_variable_get(ivar_name))
@@ -98,7 +98,8 @@ def destroy
     end
 
     def attribute_loaded?(name)
-      instance_variable_defined?("@#{name}")
+      property = self.class.properties(repository.name)[name]
+      instance_variable_defined?(property.instance_variable_name)
     end
 
     def dirty_attributes

spec/resource_spec.rb

@@ -100,7 +100,7 @@ class Planet
     # This means #attribute_loaded?'s implementation could be very
     # similar (if not identical) to:
     #   def attribute_loaded?(name)
-    #     instance_variables.include?(name.to_s.ensure_starts_with('@'))
+    #     instance_variable_defined?("@#{name}")
     #   end
     mars.attribute_loaded?(:name).should be_true
     mars.attribute_dirty?(:name).should be_true