[Vue warn]: Property "formatDate" was accessed during render but is not defined on instance.

我想用filters将后端传来的时间戳转换为日期并显示出来，但页面显示的却是奇怪的负数，并没有显示正确的日期格式，而且不管我把formatDate的函数体改成什么样，页面显示一直都是负数，感觉似乎根本没有执行函数体。vue的警告为：[Vue warn]: Property "formatDate" was accessed during render but is not defined on instance. 请问各位大佬知道要怎么解决吗？