【QT】C++线程安全的单例模板

模板代码

#pragma once
#include <mutex>
#include <atomic>

// CRTP基类模板 Curiously Recurring Template Parttern—奇异递归模板模式。
template <typename T>
class SingletonCRTP {
public:
	// 禁止拷贝构造和赋值操作
	SingletonCRTP(const SingletonCRTP&) = delete;
	SingletonCRTP& operator=(const SingletonCRTP&) = delete;

	// 禁止移动构造和赋值操作
	SingletonCRTP(SingletonCRTP&&) = delete;
	SingletonCRTP& operator=(SingletonCRTP&&) = delete;

	// 获取单例实例
	static T* getInstance() {
		if (m_instance == nullptr) {
			std::unique_lock<std::mutex> lock(m_Mutex); // 加锁
			if (m_instance == nullptr) {
				T* temp = new (std::nothrow) T();
				if (temp == nullptr) {
					throw std::bad_alloc();
				}
				m_instance = temp;
			}
		}
		return m_instance;
	}

protected:
	SingletonCRTP() = default;
	~SingletonCRTP() {
		if (m_instance) {
			delete m_instance;
			m_instance = nullptr;
		}
	}
	// 静态成员变量定义
	static T* m_instance;
	static std::mutex m_Mutex;
};

// 静态成员变量的模板类特化
template <typename T>
T* SingletonCRTP<T>::m_instance = nullptr;

template <typename T>
std::mutex SingletonCRTP<T>::m_Mutex;

使用方式

#include "SingletonCRTP.h"
class Class1 : public SingletonCRTP<Class1>
{
    friend class SingletonCRTP<Class1>;
public:
    void DoDoDo() {
        printf("Hello World!");
    }

}
int main(int argc, char *argv[])
{
	Class1::getInstance()->DoDoDo();
}