Make specifying handler easier

README.md

@@ -28,28 +28,30 @@ $ bundle
 
 ## Usage
 
-To use *Nokogiri* as a SAX handler:
+To use **Nokogiri** as a SAX handler:
 
 ```ruby
 require 'sax-machine'
 ```
 
-To use *Ox* as a SAX handler:
+To use **Ox** as a SAX handler:
 
 Add this line to your application's Gemfile:
 
 ```ruby
 gem 'ox', '>= 2.1.2'
 ```
 
-Require *Ox* handler and tell SAXMachine to use it:
+Tell SAXMachine to use Ox:
 
 ```ruby
 require 'sax-machine'
-require 'sax-machine/handlers/sax_ox_handler'
 SAXMachine.handler = :ox
 ```
 
+Please note that this operation is not thread-safe, so it's better to define
+handler at initialization stage and do not change it during runtime.
+
 ## Examples
 
 Include `SAXMachine` in any class and define properties to parse:

lib/sax-machine.rb

@@ -2,17 +2,16 @@
 require "sax-machine/sax_document"
 require "sax-machine/sax_configure"
 require "sax-machine/sax_config"
-require "sax-machine/handlers/sax_abstract_handler"
-require "sax-machine/handlers/sax_nokogiri_handler"
 
 module SAXMachine
-  @@handler = :nokogiri
-
   def self.handler
     @@handler
   end
 
   def self.handler=(handler)
+    require "sax-machine/handlers/sax_#{handler}_handler"
     @@handler = handler
   end
 end
+
+SAXMachine.handler = :nokogiri

lib/sax-machine/handlers/sax_abstract_handler.rb

@@ -1,4 +1,4 @@
-require "time"
+require 'time'
 
 module SAXMachine
   module SAXAbstractHandler

lib/sax-machine/handlers/sax_nokogiri_handler.rb

@@ -1,4 +1,5 @@
-require "nokogiri"
+require 'sax-machine/handlers/sax_abstract_handler'
+require 'nokogiri'
 
 module SAXMachine
   class SAXNokogiriHandler < Nokogiri::XML::SAX::Document

lib/sax-machine/handlers/sax_ox_handler.rb

@@ -1,4 +1,5 @@
-require "ox"
+require 'sax-machine/handlers/sax_abstract_handler'
+require 'ox'
 
 module SAXMachine
   class SAXOxHandler < Ox::Sax

spec/spec_helper.rb

@@ -15,7 +15,6 @@
 
 require File.expand_path(File.dirname(__FILE__) + '/../lib/sax-machine')
 if ENV['HANDLER'] == 'ox'
-  require 'sax-machine/handlers/sax_ox_handler'
   SAXMachine.handler = :ox
 end