how does tolua++ load a ccbi file works

cocos2d-x Lua
#1

Hi, I read the testLua example and I have some questions:
In this cocos2d-x-2.1.4\samples\Lua\TestLua\Resources\luaScript\ExtensionTest\CocosBuilderTest.lua code :

local node = CCBReaderLoad(“cocosbuilderRes/ccb/ccb/TestParticleSystems.ccbi”,proxy,true,“TestParticleSystemsLayer”)
local layer = tolua.cast(node,“CCLayer”)
if nil =\ TestParticleSystemsLayer\ then
\ local\ ccLabelTTF\ =\ tolua.cast
\ if\ nil= ccLabelTTF then
ccLabelTTF:setString(“ccb/ccb/TestParticleSystems.ccbi”)
end
end

the var mTestTitleLabelTTF is where assign a value — 这个mTestTitleLabelTTF变量时什么时候被赋值的啊，代码看不懂啊
I didn’t see this var in ccb file

#2

In the TestHeader.ccb file,you can find the mTestTitleLabelTTF which is Owner var.

#3

I learned
Thank you