refactor walker to reduce the complexity sligthly

lib/snmpjr/walker.rb

@@ -6,40 +6,41 @@ class Snmpjr
   class Walker
     def initialize opts = {}
       @target = opts.fetch(:target)
+      @session = Snmpjr::Session.new
+      @tree_utils = Snmpjr::Wrappers::Util::TreeUtils.new(@session.snmp, pdu_factory)
     end
 
     def walk oid
-      session = Snmpjr::Session.new
-      session.start
-
-      tree_utils = Snmpjr::Wrappers::Util::TreeUtils.new(session.snmp, pdu_factory)
       begin
-        response = tree_utils.getSubtree(@target, oid)
+        @session.start
+        response = @tree_utils.getSubtree(@target, oid)
       rescue Exception => e
         raise RuntimeError.new e.to_s
       ensure
-        session.close
+        @session.close
       end
-      results = response.flat_map {|response_event|
-        extract_variable_bindings(response_event)
+      response.flat_map {|response_event|
+        check_event_for_errors(response_event)
+        extract_variable_bindings(response_event.variable_bindings)
       }
-      results
     end
 
     private
 
-    def extract_variable_bindings event
+    def extract_variable_bindings variable_bindings
+      variable_bindings.flat_map {|vb|
+        Snmpjr::Response.new(value: vb.variable.to_s)
+      }
+    end
+
+    def check_event_for_errors event
       if event.is_error?
         if event.error_message == 'Request timed out.'
           raise Snmpjr::TargetTimeoutError.new('Request timed out')
         else
-          raise Snmpjr::RuntimeError.new(event.error_message)
+          raise RuntimeError.new(event.error_message)
         end
       end
-
-      event.variable_bindings.flat_map {|vb|
-        Snmpjr::Response.new(value: vb.variable.to_s)
-      }
     end
 
     def pdu_factory