C++ objects within an array inheritance

Question

I have two classes (TypeA, and TypeB) where TypeB extends TypeA.

If I create an object like so:

ATypeA* NewObject = SpawnObject<ATypeB>();

the Spawn object method just creates a new ATypeB object

and then store it in an array of TypeA, is the object within the array of TypeA or TypeB?

You only get polymorphism with pointers and references. When you assign to a regular variable, you just get the slice with that class. — Barmar
– Barmar, Commented Jun 21, 2016 at 11:12

bcolpron · Accepted Answer · 2016-06-21 11:37:07Z

2

It depends on your array and how you assign the object.

If the array is declared as TypeA myArray[10]; and you assign your object using myArray[0] = *NewObject; then the object in the array will be a sliced copy of *NewObject of type TypeA.

If the array is declared as TypeA* myArray[10]; (probably your intention) and you assign your object using myArray[0] = NewObject; then the array will contain a pointer to the same object pointed by NewObject, of course of type TypeB.

That said, you should probably consider using std::vector<std::unique_ptr<TypeA>> rather than a raw array. It will make your code simpler and safer.

edited Jun 21, 2016 at 11:37

answered Jun 21, 2016 at 11:12

bcolpron

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