[英]How to declare extern class pointers in C++?
The following is declared variable in the cpp file but I get an error, so I have conducted a research and I found that I need to declare it in the header file. 以下内容在cpp文件中声明为变量,但出现错误,因此进行了研究,发现需要在头文件中声明它。 therefore how can I declare and an extern class pointer in the header file
因此,如何在头文件中声明和extern类指针
extern AnimationController* g_pAnimationController;
Just like how you have there. 就像你在那里一样。 Ex:
例如:
// In header file:
// Declare the pointer with external linkage.
extern int* my_global_int;
// In source file:
// Define the pointer so that the linker can link stuff together with the code
// referencing the `my_global_int` symbol.
int* my_global_int = 0;
For classes and structs, if the type is unknown, then we need a forward declaration so that the compiler has some idea of what it is. 对于类和结构,如果类型未知,则需要一个前向声明,以便编译器对它的含义有所了解。 But we can combine it with the declaration, like so:
但是我们可以将其与声明结合起来,如下所示:
// In header file:
extern class AnimationController* g_pAnimationController;
Or written more verbosely: 或更详细地写:
// In header file:
class AnimationController;
extern AnimationController* g_pAnimationController;
Update for comment question: 更新评论问题:
#include <map>
#include <string>
// Declare AnimationCallback
extern std::map<std::string, AnimationCallback*> g_mCallbackMap;
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