帮忙看看,这个是怎么一回事?
D100 2004-05-12 10:29:45 好像没理由的呀。
#include <string>
#include <iostream>
using namespace std;
class Singleton {
public:
static Singleton* instance() {
if (instance_ == 0)
instance_ = new Singleton;
return instance_;
}
void print() { std::cout << "Hello World" << std::endl;}
private:
static Singleton* instance_;
};
int main()
{
Singleton::instance()->print();
system("PAUSE");
}
[Linker error] undefined reference to `Singleton::instance_'