instance method call

# File railties/lib/rails/rack/static.rb, line 13
      def call(env)
        path        = env['PATH_INFO'].chomp('/')
        method      = env['REQUEST_METHOD']

        if FILE_METHODS.include?(method)
          if file_exist?(path)
            return @file_server.call(env)
          else
            cached_path = directory_exist?(path) ? "#{path}/index" : path
            cached_path += ::ActionController::Base.page_cache_extension

            if file_exist?(cached_path)
              env['PATH_INFO'] = cached_path
              return @file_server.call(env)
            end
          end
        end

        @app.call(env)
      end