How to use polymorphism to access derived class vector member from base class?

Question

It\'s said that with polymorphism, we can access a derived class member field with it\'s base class object like this:

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Answer 1

Runtime polymorphism in C++, achieved via virtual functions, works on covariant types. The only covariant types are pointers and references. Since you have a vector<Tool>, you lose polymorphism. To retain it, store a vector<Tool*>. Even better, store a vector<unique_ptr<Tool>>.

Assigning a derived class object to a base class is called object slicing. You do lose information contained in the derived object. This is the case when you are inserting a Computer into a vector<Tool>.