Added default group policy

group.go

@@ -1,36 +1,26 @@
 package graphvent
 
 import (
-  "encoding/json"
 )
 
-type GroupExt struct {
-  Members map[NodeID]string `gv:"members"`
-}
+var GroupReadPolicy = NewAllNodesPolicy(Tree{
+  SerializedType(ReadSignalType): {
+    SerializedType(GroupExtType): {
+      Hash(FieldNameBase, "members"): nil,
+    },
+  },
+})
 
-func (ext *GroupExt) Type() ExtType {
-  return GroupExtType
-}
-
-func (ext *GroupExt) MarshalBinary() ([]byte, error) {
-  return json.Marshal(ext)
+type GroupExt struct {
+  Members []NodeID `gv:"members"`
 }
 
-func NewGroupExt(members map[NodeID]string) *GroupExt {
-  if members == nil {
-    members = map[NodeID]string{}
-  }
-
+func NewGroupExt(members []NodeID) *GroupExt {
   return &GroupExt{
     Members: members,
   }
 }
 
-func (ext *GroupExt) Deserialize(ctx *Context, data []byte) error {
-  ext.Members = map[NodeID]string{}
-  return json.Unmarshal(data, ext)
-}
-
 func (ext *GroupExt) Process(ctx *Context, node *Node, source NodeID, signal Signal) Messages {
   return nil
 }

policy.go

@@ -137,7 +137,7 @@ func (policy MemberOfPolicy) Allows(ctx *Context, principal_id NodeID, action Tr
     if id == node.ID {
       ext, err := GetExt[*GroupExt](node, GroupExtType)
       if err == nil {
-        for member := range(ext.Members) {
+        for _, member := range(ext.Members) {
           if member == principal_id {
             if rule.Allows(action) == Allow {
               return nil, Allow