couldn't get cmd pointer (substituting NULL): extracting data from value failed Couldn't materialize

今天再调试程序的时候 po 一个变量出现这个错误  

couldn't get cmd pointer (substituting NULL): extracting data from value failed Couldn't materialize

其他的可以进行 网上查了一下 说是工程编译的目标类型是release 应该是debug  解决方法很简单 ： product－－scheme －－ Edit Scheme －－在红色的地方选择上Debug就可以了