Преобразование из производного ** в базу **
я читалэто и, к сожалению, не мог глубоко понять, почему компилятор не разрешает преобразование из Derived ** в Base **. Также я виделэто который дает не больше информации, чем ссылка на parashift.com.
РЕДАКТИРОВАТЬ:
Давайте проанализируем этот код построчно:
Car car;
Car* carPtr = &car;
Car** carPtrPtr = &carPtr;
//MyComment: Until now there is no problem!
Vehicle** vehiclePtrPtr = carPtrPtr; // This is an error in C++
//MyComment: Here compiler gives me an error! And I try to understand why.
//MyComment: Let us consider that it was allowed. So what?? Let's go ahead!
NuclearSubmarine sub;
NuclearSubmarine* subPtr = ⊂
//MyComment: this two line are OK too!
*vehiclePtrPtr = subPtr;
//MyComment: the important part comes here... *vehiclePtrPtr is a pointer to
//MyComment: a vehicle, particularly in our case it points to a Car object.
//MyComment: Now when I assign to the pointer to the Car object *vehiclePtrPtr,
//MyComment: a pointer to NuclearSubmarine, then it should just point to the
//MyComment: NuclearSubmarine object as it is indeed a pointer to a Vehicle,
//MyComment: isn't it? Where is my fault? Where I am wrong?
// This last line would have caused carPtr to point to sub!
carPtr->openGasCap(); // This might call fireNuclearMissle()!