Further refactoring and bugfixing.

app/models/concerns/has_groups.rb

@@ -7,8 +7,8 @@ module HasGroups
 
     attr_accessor :group_access_buffer
 
-    after_create :check_group_access_buffer
-    after_update :check_group_access_buffer
+    after_create :process_group_access_buffer
+    after_update :process_group_access_buffer
 
     association_attributes_ignored :groups, group_through_identifier
 
@@ -212,16 +212,12 @@ module HasGroups
 
   def groups_access_map_store(map)
     fill_group_access_buffer do
-      map.each do |group_identifier, accesses|
+      Hash(map).each do |group_identifier, accesses|
         # use given key as identifier or look it up
         # via the given block which returns the identifier
         group_id = block_given? ? yield(group_identifier) : group_identifier
 
-        if !accesses.is_a?(Array)
-          accesses = [accesses]
-        end
-
-        accesses.each do |access|
+        Array(accesses).each do |access|
           push_group_access_buffer(
             group_id: group_id,
             access:   access
@@ -234,14 +230,14 @@ module HasGroups
   def fill_group_access_buffer
     @group_access_buffer = []
     yield
-    check_group_access_buffer if id
+    process_group_access_buffer if id
   end
 
   def push_group_access_buffer(entry)
     @group_access_buffer.push(entry)
   end
 
-  def flushed_group_access_buffer
+  def flush_group_access_buffer
     # group_access_buffer is at least an empty Array
     # if changes to the map were performed
     # otherwise it's just an update of other attributes
@@ -251,9 +247,9 @@ module HasGroups
     cache_delete
   end
 
-  def check_group_access_buffer
+  def process_group_access_buffer
 
-    flushed_group_access_buffer do
+    flush_group_access_buffer do
       destroy_group_relations
 
       break if group_access_buffer.blank?