class Singleton1
{
public:
Singleton1& Instance()
{
static Singleton Obj;
return Obj;
private:
Singleton1();
}
}
优雅的解决了问题。
再看一个可扩展的。
#include
#include
class SingletonBase
{
public:
SingletonBase() { cout << "SingletonBase created!" << endl; }
virtual ~SingletonBase() { cout << "SingletonBase destroyed!" << endl; }
virtual void Access() { cout << "SingletonBase accessed!" << endl; }
static SingletonBase* GetObj() { return m_pObj; }
static void SetObj(SingletonBase* pObj) { m_pObj = pObj; }
protected:
static SingletonBase* m_pObj;
};
SingletonBase* SingletonBase::m_pObj;
inline SingletonBase* Base()
{
assert(SingletonBase::GetObj());
return SingletonBase::GetObj();
}
// Create a derived singleton-type class
class SingletonDerived : public SingletonBase
{
public:
SingletonDerived()
{ cout << "SingletonDerived created!" << endl; }
virtual ~SingletonDerived()
{ cout << "SingletonDerived destroyed" << endl; }
virtual void Access()
{ cout << "SingletonDerived accessed!" << endl; }
protected:
};
inline SingletonDerived* Derived()
{
assert(SingletonDerived::GetObj());
return (SingletonDerived*)SingletonDerived::GetObj();
}
// Using the code...
// The complex singleton requires more work to use, but is
// more flexible. It also allows more control over object
// creation, which is sometimes desirable.
SingletonDerived::SetObj(new SingletonDerived);
// Notice that the functionality has been overridden by the new
// class, even though accessing it through the original method.
Base()->Access();
Derived()->Access();
// This variation on a singleton unfortunately requires both
// explicit creation and deletion.
delete SingletonDerived::GetObj();
一个可扩展的singleton。
主要用于需要大量访问的全局对象。
