|
方法一：
namespace designpattern_singleton
{
// class singleton
class singleton
{
protected:
singleton() {}
static singleton *_instance ;
private:
singleton(const singleton&) ;
singleton& operator=(const singleton&) ;
} ;
singleton* singleton::_instance = null ;
// class concretesingleton
class concretesingleton : public singleton
{
public:
static singleton* instance() ;
protected:
concretesingleton() {}
} ;
singleton* concretesingleton::instance()
{
(_instance == null) ? _instance = new concretesingleton() : 0 ;
return _instance ;
}
}
客户端代码：
{
using namespace designpattern_singleton ;
singleton *p = concretesingleton::instance() ;
}
方法二：
namespace designpattern_singleton
{
// class singleton
class singleton
{
protected:
singleton() {}
private:
singleton(const singleton&) ;
singleton& operator=(const singleton&) ;
} ;
// class concretesingleton
class concretesingleton : public singleton
{
public:
static singleton* instance() { static concretesingleton _instance ; return &_instance ; }
protected:
concretesingleton() {}
} ;
}
客户端代码：
{
using namespace designpattern_singleton ;
singleton *p = concretesingleton::instance() ;
}
方法三：
namespace designpattern_singleton
{
template < class t >
class singleton
{
public:
static t* instance() { static t _instance ; return &_instance ; }
protected:
singleton() {}
private:
singleton(const singleton &) ;
singleton& operator=(const singleton&) ;
} ;
class concretesingleton : public singleton< concretesingleton > {} ;
}
客户端代码
{
using namespace designpattern_singleton ;
concretesingleton *p = concretesingleton::instance() ;
} | 
