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Runtime Polymorphism · 4:39
Hierarchies, Virtual Destructors and Slicing
A Smiley is a Circle is a Shape. We watch such an object being built from the base up and torn down from the top, see why deleting it through a Shape pointer needs a virtual destructor, use dynamic_cast to ask what an object really is, and meet two ways a base class quietly cuts an object short: slicing on copy, and indexing an array of Circles through a Shape pointer.
You will learn
- Predict the order of constructors and destructors in a class hierarchy
- Explain why a polymorphic base class needs a virtual destructor
- Use dynamic_cast with pointers and references and handle failure
- Recognise slicing and the array-through-base-pointer bug, and avoid both