Convenient cache and content type for response generation

These three convenient methods make it easy to declaratively specify how a response should be structured. For example:

    response.do_not_cache!

    response.cache!

    response.content_type! 'text/html'

Open to discussion w.r.t. naming, and behaviour. I monkey patch these in which might be fine for my usage, but I thought it could be useful to a wider audience.

lib/rack.rb

@@ -38,6 +38,7 @@ def self.release
   SERVER_ADDR       = 'SERVER_ADDR'.freeze
   SERVER_PORT       = 'SERVER_PORT'.freeze
   CACHE_CONTROL     = 'Cache-Control'.freeze
+  EXPIRES           = 'Expires'.freeze
   CONTENT_LENGTH    = 'Content-Length'.freeze
   CONTENT_TYPE      = 'Content-Type'.freeze
   SET_COOKIE        = 'Set-Cookie'.freeze

lib/rack/response.rb

@@ -168,6 +168,25 @@ def set_cookie(key, value)
       def delete_cookie(key, value={})
         set_header SET_COOKIE, ::Rack::Utils.add_remove_cookie_to_header(get_header(SET_COOKIE), key, value)
       end
+
+      # Specifies that the content shouldn't be cached. Overrides `cache!` if already called.
+      def do_not_cache!
+        set_header CACHE_CONTROL, "no-cache, must-revalidate"
+        set_header EXPIRES, Time.now.httpdate
+      end
+
+      # Specify that the content should be cached.
+      def cache!(duration = 3600)
+        unless headers[CACHE_CONTROL] =~ /no-cache/
+          set_header CACHE_CONTROL, "public, max-age=#{duration}"
+          set_header EXPIRES, (Time.now + duration).httpdate
+        end
+      end
+
+      # Specify the content type of the response data.
+      def content_type!(value)
+        set_header CONTENT_TYPE, value.to_s
+      end
     end
 
     include Helpers