单例模式 c++

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 饿汉式：在定义单例类时就实例化。

（一定是线程安全的）

#include<iostream>

using namespace std;

class single
{

private:
	single() {
		cout << "construct .." << endl;
	};
	static single* instance;


public:
	static single *get_instance() {
		cout << "get_instance" << endl;
		return instance;
	}
};

single * single::instance = new single();
int main(int argc, char const *argv[])
{
	single *s;
	s->get_instance();
	single *s1 = single::get_instance();

	system("pause");
	return 0;
}