make loading more private and less presumptive

lib/stringex.rb

@@ -3,10 +3,9 @@
 require 'stringex/configuration'
 require 'stringex/string_extensions'
 require 'stringex/unidecoder'
+require 'stringex/acts_as_url'
 
 String.send :include, Stringex::StringExtensions::PublicInstanceMethods
 String.send :extend, Stringex::StringExtensions::PublicClassMethods
 
-require 'stringex/acts_as_url' if defined?(ActiveRecord) || defined?(Mongoid::Document)
-
-ActiveRecord::Base.send :include, Stringex::ActsAsUrl if defined?(ActiveRecord)
+Stringex::ActsAsUrl.load_adapters

lib/stringex/acts_as_url.rb

@@ -4,10 +4,20 @@
 
 module Stringex
   module ActsAsUrl # :nodoc:
+    ADAPTERS = [
+      Adapter::ActiveRecord
+    ]
+
     def self.included(base)
       base.extend ClassMethods
     end
 
+    def self.load_adapters
+      ADAPTERS.each do |adapter|
+        adapter.load if adapter.loadable?
+      end
+    end
+
     module ClassMethods # :doc:
       # Creates a callback to automatically create an url-friendly representation
       # of the <tt>attribute</tt> argument. Example:

lib/stringex/acts_as_url/adapter/active_record.rb

@@ -28,6 +28,15 @@ def url_attribute(instance)
           end
         end
 
+        def self.loadable?
+          defined? ActiveRecord
+        end
+
+        def self.load
+          ensure_loadable
+          ::ActiveRecord::Base.send :include, Stringex::ActsAsUrl
+        end
+
       private
 
         def add_new_record_url_owner_conditions

lib/stringex/acts_as_url/adapter/base.rb

@@ -5,6 +5,7 @@ class Base
         attr_accessor :base_url, :configuration, :instance, :klass, :settings
 
         def initialize(configuration)
+          ensure_loadable
           self.configuration = configuration
           self.settings = configuration.settings
         end
@@ -24,14 +25,24 @@ def initialize_urls!(klass)
           end
         end
 
-      private
+        def self.available?
+          false
+        end
 
-        # Override any of these you need within your adapter
+        def self.ensure_loadable
+          raise "#{self} is not an loadable adapter" unless loadable?
+        end
+
+      private
 
         def duplicate_for_base_url(n)
           "#{base_url}#{settings.duplicate_count_separator}#{n}"
         end
 
+        def ensure_loadable
+          self.class.ensure_loadable
+        end
+
         def handle_duplicate_url!
           return if url_owners.none?{|owner| url_attribute_for(owner) == base_url}
           n = 1
@@ -47,6 +58,10 @@ def handle_url!
           write_url_attribute base_url
         end
 
+        def loadable?
+          self.class.loadable?
+        end
+
         def modify_base_url
           root = instance.send(settings.attribute_to_urlify).to_s
           self.base_url = root.to_url(configuration.string_extensions_settings)