This means that the type parameter must support comparison with other instances of its own type, via the Comparable interface. An example of such a class is provided in the Oracle tutorial Object Ordering. Note the similar pattern to T extends Comparable<T> in the excerpt below:
Your SortedContainerImpl class has two separate Container base classes. One is virtual (via the SortedContainer class) and the other is non-virtual (via the ContainerImpl class). SortedContainerImpl has concrete implementations of Container::get_size() and Container::get(int) for the base that comes in from ContainerImpl, but not for the virtual base that comes in via SortedContainer. One way to … Read more
The clearest way to express polymorphism is via an abstract base class (or interface) This class is abstract because the goPee() method is not definable for Humans. It is only definable for the subclasses Male and Female. Also, Human is an abstract concept — You cannot create a human that is neither Male nor Female. It’s got … Read more
Polymorphism is one of the tenets of Object Oriented Programming (OOP). It is the practice of designing objects to share behaviors and to be able to override shared behaviors with specific ones. Polymorphism takes advantage of inheritance in order to make this happen. In OOP everything is considered to be modeled as an object. This … Read more
They can result if you try to make a virtual function call from a constructor or destructor. Since you can’t make a virtual function call from a constructor or destructor (the derived class object hasn’t been constructed or has already been destroyed), it calls the base class version, which in the case of a pure … Read more
If you think about the Greek roots of the term, it should become obvious. Poly = many: polygon = many-sided, polystyrene = many styrenes (a), polyglot = many languages, and so on. Morph = change or form: morphology = study of biological form, Morpheus = the Greek god of dreams able to take any form. So … Read more
Virtual destructors are useful when you might potentially delete an instance of a derived class through a pointer to base class: Here, you’ll notice that I didn’t declare Base’s destructor to be virtual. Now, let’s have a look at the following snippet: Since Base’s destructor is not virtual and b is a Base* pointing to … Read more
Here is how I understood not just what virtual functions are, but why they’re required: Let’s say you have these two classes: In your main function: So far so good, right? Animals eat generic food, cats eat rats, all without virtual. Let’s change it a little now so that eat() is called via an intermediate function (a trivial function just … Read more