Qt 报错 use of undeclared identifier 'cast'

cannot initialize object parameter of type 'QObject' with an expression of type of scanner

use of undeclared identifier 'cast'

包含unordered_map这个头文件了没有
using namespace std;了没有
或者是你的c++编译器版本低

https://blog.csdn.net/ydlchina/article/details/88638169