- elmenth_path raise an ActiveResource::MissingPrefixParam exception when prefix_options does not has all required prefix_options ex: class StreetAddress < ActiveResource::Base self.site = "http://37s.sunrise.i:3000/people/:person_id/" end

StreetAddress.element_path(1)
    # => ActiveResource::MissingPrefixParam

activeresource/lib/active_resource/base.rb

@@ -621,6 +621,12 @@ module ActiveResource
       #   # => /posts/5/comments/1.xml?active=1
       #
       def element_path(id, prefix_options = {}, query_options = nil)
+
+        p_options = HashWithIndifferentAccess.new(prefix_options)
+        prefix_parameters.each do |p|
+          raise MissingPrefixParam if p_options[p].blank?
+        end
+
         prefix_options, query_options = split_options(prefix_options) if query_options.nil?
         "#{prefix(prefix_options)}#{collection_name}/#{URI.escape id.to_s}.#{format.extension}#{query_string(query_options)}"
       end

activeresource/lib/active_resource/exceptions.rb

@@ -36,6 +36,9 @@ module ActiveResource
     def to_s; response['Location'] ? "#{super} => #{response['Location']}" : super; end
   end
 
+  # Raised when ...
+  class MissingPrefixParam < ArgumentError; end # :nodoc:
+
   # 4xx Client Error
   class ClientError < ConnectionError; end # :nodoc:
 

activeresource/test/cases/base_test.rb

@@ -475,6 +475,12 @@ class BaseTest < Test::Unit::TestCase
     assert_equal '/people/ann%20mary/addresses/ann%20mary.xml', StreetAddress.element_path(:'ann mary', 'person_id' => 'ann mary')
   end
 
+  def test_custom_element_path_without_parent_id
+    assert_raise ActiveResource::MissingPrefixParam do
+      assert_equal '/people/1/addresses/1.xml', StreetAddress.element_path(1)
+    end
+  end
+
   def test_module_element_path
     assert_equal '/sounds/1.xml', Asset::Sound.element_path(1)
   end
@@ -560,6 +566,8 @@ class BaseTest < Test::Unit::TestCase
       assert_equal Set.new([:the_param1]), person_class.prefix_parameters
       person_class.prefix = "the_prefix/:the_param2"
       assert_equal Set.new([:the_param2]), person_class.prefix_parameters
+      person_class.prefix = "the_prefix/:the_param1/other_prefix/:the_param2"
+      assert_equal Set.new([:the_param2, :the_param1]), person_class.prefix_parameters
     end
   end
 

activeresource/test/cases/finder_test.rb

@@ -84,7 +84,7 @@ class FinderTest < Test::Unit::TestCase
 
   def test_find_by_id_not_found
     assert_raise(ActiveResource::ResourceNotFound) { Person.find(99) }
-    assert_raise(ActiveResource::ResourceNotFound) { StreetAddress.find(1) }
+    assert_raise(ActiveResource::ResourceNotFound) { StreetAddress.find(99, :params => {:person_id => 1}) }
   end
 
   def test_find_all_sub_objects