c++ - 'Population' has not been declared

Question

我有两个类Population和Group，因为要写一个Group的成员函数

void initialize(Population<T> &p, const int id);

但我已经加载了Population的头文件，IDE却提示我Population' has not been declared，请问这是什么情况？？

这是Population的内容和位置

Answer 1

includeThe paths all start from the current path. The picture you showed is a bit unclear. But based on the image information, I wrote it down. You can try it.

Answer 2

The problem has been solved because the Group file is already included in Population.h. So declare the Population class above the Group class and you can use it. .