Lua内存泄漏：三类最常见的滞留

-- 错误：开界面挂监听，关界面不摘
function openPanel()
    on("tick", function()
        refreshPanel()
    end)
end

local function openPanel()
    local handler = function()
        refreshPanel()
    end
    on("tick", handler)
    setplayvar(me, "tickHandler", handler)
end
local function closePanel()
    local h = getplayvar(me, "tickHandler")
    if h then
        off("tick", h)
        setplayvar(me, "tickHandler", nil)
    end
end