单例的实现

1 :test.h 声明

class SerialPort : public QObject
{
	Q_OBJECT

public:
	explicit SerialPort(QObject* parent = nullptr);
	~SerialPort();
	static int CreateInstance();
	static void DestroyInstance();
	//单例
	static SerialPort* instance()
	{
		return m_instance;
	}
	private:
	static SerialPort* m_instance;
};

2 :test.cpp 定义

//静态变量使用前必须初始化
SerialPort* SerialPort::m_instance = nullptr;

//创建单例
int SerialPort::CreateInstance()
{
	SerialPort::m_instance = new SerialPort;
	if (m_instance != nullptr)
	{
		return 0;
	}
	else
	{
		return -1;
	}
}
//销毁单例
void SerialPort::DestroyInstance()
{
	if (m_instance)
	{
		delete m_instance;
		m_instance = NULL;
	}
}

3 ：main.cpp 使用

//实例化单例
	m_attenSerialPort = SerialPort::instance();
//使用单例
	QStringList portNameList = m_attenSerialPort->GetAvaliablePortNameList();
//摧毁单例
   SerialPort::DestroyInstance();