用宏实现的单例模式（转）

[u011022940]

个人感觉使用比较方便
#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();

[这不是鸭头]