Simplify access to router_name using the existing scope lookup.

app/controllers/devise/registrations_controller.rb

@@ -112,7 +112,8 @@ class Devise::RegistrationsController < DeviseController
   # The path used after sign up for inactive accounts. You need to overwrite
   # this method in your own RegistrationsController.
   def after_inactive_sign_up_path_for(resource)
-    router_name = Devise::Mapping.find_mapping!(resource).router_name
+    scope = Devise::Mapping.find_scope!(resource)
+    router_name = Devise.mappings[scope].router_name
     context = router_name ? send(router_name) : self
     context.respond_to?(:root_path) ? context.root_path : "/"
   end

lib/devise/controllers/helpers.rb

@@ -101,9 +101,9 @@ module Devise
       # The scope root url to be used when they're signed in. By default, it first
       # tries to find a resource_root_path, otherwise it uses the root_path.
       def signed_in_root_path(resource_or_scope)
-        mapping = Devise::Mapping.find_mapping!(resource_or_scope)
-        scope = mapping.scope
-        router_name = mapping.router_name
+        scope = Devise::Mapping.find_scope!(resource_or_scope)
+        router_name = Devise.mappings[scope].router_name
+
         home_path = "#{scope}_root_path"
 
         context = router_name ? send(router_name) : self
@@ -157,7 +157,8 @@ module Devise
       #
       # By default it is the root_path.
       def after_sign_out_path_for(resource_or_scope)
-        router_name = Devise::Mapping.find_mapping!(resource_or_scope).router_name
+        scope = Devise::Mapping.find_scope!(resource_or_scope)
+        router_name = Devise.mappings[scope].router_name
         context = router_name ? send(router_name) : self
         context.respond_to?(:root_path) ? context.root_path : "/"
       end

lib/devise/controllers/url_helpers.rb

@@ -46,9 +46,8 @@ module Devise
 
               class_eval <<-URL_HELPERS, __FILE__, __LINE__ + 1
                 def #{method}(resource_or_scope, *args)
-                  mapping = Devise::Mapping.find_mapping!(resource_or_scope)
-                  scope = mapping.scope
-                  router_name = mapping.router_name
+                  scope = Devise::Mapping.find_scope!(resource_or_scope)
+                  router_name = Devise.mappings[scope].router_name
                   context = router_name ? send(router_name) : _devise_route_context
                   context.send("#{action}\#{scope}_#{module_name}_#{path_or_url}", *args)
                 end

lib/devise/mapping.rb

@@ -43,23 +43,6 @@ module Devise
       raise "Could not find a valid mapping for #{obj.inspect}"
     end
 
-    # Receives an object and find a mapping for it, then return the routing
-    # details associated with the mapping. If a scope cannot be found,
-    # raises an error.
-    def self.find_mapping!(obj)
-      case obj
-        when String, Symbol
-          scope = obj.to_sym
-          Devise.mappings.each_value { |m| return RoutingDetails.new(m) if m.name == scope }
-        when Class
-          Devise.mappings.each_value { |m| return RoutingDetails.new(m) if obj <= m.to }
-        else
-          Devise.mappings.each_value { |m| return RoutingDetails.new(m) if obj.is_a?(m.to) }
-      end
-
-      raise "Could not find a valid mapping for #{obj.inspect}" unless mapping
-    end
-
     def self.find_by_path!(path, path_type=:fullpath)
       Devise.mappings.each_value { |m| return m if path.include?(m.send(path_type)) }
       raise "Could not find a valid mapping for path #{path.inspect}"