类模板的静态成员初始化

Question

Please find the code below:

#include <iostream>
using namespace std;
template<typename T>
class A
{
    static A* self;
};

template<typename T>
A* A<T>::self = NULL;
int main()
{
    return 0;
}

I am facing a compilation problem while initialising the static pointer. Even though so many links has said the same way (the way i initialised) but still the problem resist. Below is the compilation error.

"expected constructor, destructor, or type conversion before '*' token"

Answer 1

A is a class template, so you need to specify the template parameter when defining the pointer to it.

Instead of:

template<typename T>
A* A<T>::self = NULL;

it should be:

template<typename T>
A<T>* A<T>::self = NULL;

Within the class body, specifying the template parameter is optional, so you can write A* there and it will be treated the same as A<T> * .

Answer 2

尝试：

template<typename T> A<T>* A<T>::self = NULL;