Defer user_model load so it can be a constant

lib/clearance/configuration.rb

@@ -1,20 +1,14 @@
 module Clearance
   class Configuration
-    attr_accessor :mailer_sender, :cookie_expiration, :password_strategy, :user_model_name
+    attr_accessor :mailer_sender, :cookie_expiration, :password_strategy, :user_model
 
     def initialize
       @mailer_sender     = 'donotreply@example.com'
       @cookie_expiration = lambda { 1.year.from_now.utc }
-      @user_model_name   = '::User'
-    end
-
-    def user_model_name=(model_name)
-      @user_model_name = model_name
-      @user_model      = nil
     end
 
     def user_model
-      @user_model ||= @user_model_name.constantize
+      @user_model || ::User
     end
   end
 
@@ -35,7 +29,7 @@ class << self
   #     config.mailer_sender     = 'me@example.com'
   #     config.cookie_expiration = lambda { 2.weeks.from_now.utc }
   #     config.password_strategy = MyPasswordStrategy
-  #     config.user_model_name   = 'MyNamespace::MyUser'
+  #     config.user_model        = MyNamespace::MyUser
   #   end
   def self.configure
     self.configuration ||= Configuration.new

spec/configuration_spec.rb

@@ -14,16 +14,15 @@
 
   describe "when a custom user_model_name is specified" do
     before do
+      MyUser = Class.new
       Clearance.configure do |config|
-        config.user_model_name = 'MyUser'
+        config.user_model = MyUser
       end
-
-      MyUser = Class.new
     end
 
     after do
       Clearance.configure do |config|
-        config.user_model_name = '::User'
+        config.user_model = ::User
       end
     end