When we create a node child for a layer and extend some attributes value,we can do as follow:
@
local node = cc.Node:create()
node.extendValue1 = 10000
layerParent:addChild(node,0,9999)
@
When we wan to get this node and its extend attribute value somewhere, we can do as follow:
@
local child = layerParent:getChildByTag(9999)
print(child.extendValue1)
@
Sometimes we will get 10000,and sometimes we will get nil. Because the lua gc event collect the node value,so when we call getChildByTag,it create a new usedata and the extend attribute value is nil.

To avoid the Object userdata to gc collect, we add the Object data to a global table to keep refrence, and when the destructor of releated object called,the refrence will be removed from this global table.In this way, we can use extended userdata attributes trustingly.