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[26] [27] In C++, an abstract class is a class having at least one abstract method given by the appropriate syntax in that language (a pure virtual function in C++ parlance). [25] A class consisting of only pure virtual methods is called a pure abstract base class (or pure ABC) in C++ and is also known as an interface by users of the language. [13]
The class A serves as a base class for the derived class B, which in turn serves as a base class for the derived class C. The class B is known as intermediate base class because it provides a link for the inheritance between A and C. The chain ABC is known as inheritance path. A derived class with multilevel inheritance is declared as follows:
In class-based object-oriented programming, abstract types are implemented as abstract classes (also known as abstract base classes), and concrete types as concrete classes. In generic programming , the analogous notion is a concept , which similarly specifies syntax and semantics, but does not require a subtype relationship: two unrelated ...
The C++ examples in this section demonstrate the principle of using composition and interfaces to achieve code reuse and polymorphism. Due to the C++ language not having a dedicated keyword to declare interfaces, the following C++ example uses inheritance from a pure abstract base class.
Room is the base class for a final product (MagicRoom or OrdinaryRoom). MazeGame declares the abstract factory method to produce such a base product. MagicRoom and OrdinaryRoom are subclasses of the base product implementing the final product.
As an example, an abstract base class MathSymbol may provide a pure virtual function doOperation(), and derived classes Plus and Minus implement doOperation() to provide concrete implementations. Implementing doOperation() would not make sense in the MathSymbol class, as MathSymbol is an abstract concept whose behaviour is defined solely for ...
Python allows programmers to define their own types using classes, most often used for object-oriented programming. New instances of classes are constructed by calling the class (for example, SpamClass or EggsClass ()), and the classes are instances of the metaclass type (itself an instance of itself), allowing metaprogramming and reflection.
The class defines the data format or type (including member variables and their types) and available procedures (class methods or member functions) for a given type or class of object. Objects are created by calling a special type of method in the class known as a constructor .