Lua __index链：属性查找的逐层开销

-- 错误：热循环里每帧走完整查找链
function onFrame(node)
    local bar = node.root:getChildByName("hpbar")
end

local function getNode(panel, key)
    local cache = rawget(panel, "_cache")
    if cache == nil then
        cache = {}
        rawset(panel, "_cache", cache)
    end
    local n = cache[key]
    if n == nil then
        n = panel.root:getChildByName(key)
        cache[key] = n
    end
    return n
end
local p = getplayerbyname("idx01")
sendmsg(p, 1, "首次深查找，之后直读缓存")