Bug About ComponentLua

cocos2d-x Lua
1

Hierarchy of nodes:

MainScene
|----Parent
|----|----Child

Codes

ParentCom.lua

local M = {}
function M:printSelf()
    cc.log("This is Parent");
end
return M

ChildCom.lua

local M = {}
function M:printSelf()
    print("This is Child");
end
return M

MainScene.lua

local root = self:getResourceNode()
    local parent = root:getChildByName("Parent")
    local child = parent:getChildByName("Child")

    local parentCom = cc.ComponentLua:create("app/views/ParentCom.lua")
    parentCom:setName("ParentComponent")
    parent:addComponent(parentCom)

    local childCom = cc.ComponentLua:create("app/views/ChildCom.lua")
    childCom:setName("ChildComponent")
    child:addComponent(childCom)

    parentCom:printSelf()

Then the parentCom:printSelf() output is This is Child:. Why does this happen?