fix registering on_add() callbacks. colyseus/colyseus#915

Author: endel

colyseus/serializer/schema/callbacks.lua

@@ -208,9 +208,15 @@ function Callbacks:add_callback_or_wait_collection_available(instance, field_nam
   local remove_handler = function() end
   local remove_callback = function() remove_handler() end
   if instance[field_name] == nil then
-    remove_handler = _self:listen(instance, field_name, function(collection, _)
-      remove_handler = _self:add_callback(collection.__refid, operation, callback)
+    local remove_property_callback
+    remove_property_callback = _self:listen(instance, field_name, function(collection, _)
+      if collection ~= nil then
+        -- Remove the property listener now that collection is available
+        remove_property_callback()
+        remove_handler = _self:add_callback(collection.__refid, operation, callback)
+      end
     end)
+    remove_handler = remove_property_callback
     return remove_callback
   else
     -- immediately trigger callback for each item in the collection

example/main.script

@@ -38,11 +38,11 @@ local function join_my_room()
             end)
 
             callbacks:listen(player, "x", function(value, previous_value)
-                print("[MyRoom] player.x changed: " .. tostring(value) .. " => " .. tostring(previous_value))
+                print("[MyRoom] player.x changed: " .. tostring(previous_value) .. " => " .. tostring(value))
             end)
 
             callbacks:listen(player, "y", function(value, previous_value)
-                print("[MyRoom] player.y changed: " .. tostring(value) .. " => " .. tostring(previous_value))
+                print("[MyRoom] player.y changed: " .. tostring(previous_value) .. " => " .. tostring(value))
             end)
 
             callbacks:listen(player, "disconnected", function(value, previous_value)

release.json

@@ -1,3 +1,3 @@
 {
-    "version": "0.17.2"
+    "version": "0.17.3"
 }