重发试试：A Polymorphic Product Creator.

I have create a article about this topic, but the all lettles pile together, so I rewrite it again. I create a polymorphic product creator which allows you to create objects using its name as a template argument, return a pointer to the object with its base class type. Here is the implementation: template struct AbstractCreator { virtual AbstractCreator* operator()(){throw();return 0;} }; Because we don't want to create a object which is base typed that unsually is a abstruct class, we have to prevent the creator from calling the function AbstractCreator::operator()().But we can not make it a pure function, the reason for which I will point out in the next article . template class CreatePolicy = Loki::CreateUsingNew > struct ProductCreator: public AbstructCreator { AbstructCreator* operator()() { return CreatePolicy::Create();} }; The code is so few but not so easy to understand. Let's have a view about how the creator works: We assum that class GTank and GBullet are derived from class GObject,then we can create codes like this: GObject* pO1 = ProductCreator()(); GObject* pO2 = ProductCreator()(); Why we need a ProductCreator? There are two reasons.