用宏实现的单例模式

#define SINGLETON_CLASS_NO_DEF_CONSTRUCT_BODY(class_name)\
    private:\
    class_name();\
    class_name(const class_name&);\
    class_name & operator = (const class_name &);\
    public:\
    static class_name & Instance()\
        {\
        static class_name one;\
        return one;\
        }

#define SINGLETON_CLASS(class_name)\
    private:\
    class_name(){}\
    class_name(const class_name&);\
    class_name & operator = (const class_name &);\
    public:\
    static class_name & Instance()\
        {\
        static class_name one;\
        return one;\
        }

两个宏的区别仅在于是否实现 默认的无参构造函数。使用例子：

// HostBasicInformation.h
class HostBasicInformation
{
	SINGLETON_CLASS_NO_DEF_CONSTRUCT_BODY(HostBasicInformation)

public:
	virtual ~HostBasicInformation();
	
	std::string GetInstallCode();
	
};

// HostBasicInformation.cpp

// 若使用SINGLETON_CLASS ，则不需要自己定义无参构造函数
HostBasicInformation::HostBasicInformation(){

}



HostBasicInformation::~HostBasicInformation(){

}

std::string HostBasicInformation::GetInstallCode()
{
	return "";
}

这种宏的方式，主要优点在于：能严格限制此类的使用方式，也就是只能当做单例来使用。

std::string str_installCode = HostBasicInformation::Instance().GetInstallCode();