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A class in C++ is a user-defined type or data structure declared with any of the keywords class, struct or union (the first two are collectively referred to as non-union classes) that has data and functions (also called member variables and member functions) as its members whose access is governed by the three access specifiers private, protected or public.
A friend function is declared by the class that is granting access, so friend functions are part of the class interface, like methods. Friend functions allow alternative syntax to use objects, for instance f(x) instead of x.f(), or g(x,y) instead of x.g(y). Friend functions have the same implications on encapsulation as methods.
/*Ruby has three member variable types: class, class instance, and instance. */ class Dog # The class variable is defined within the class body with two at-signs # and describes data about all Dogs *and* their derived Dog breeds (if any) @@sniffs = true end mutt = Dog. new mutt. class. sniffs #=> true class Poodle < Dog # The "class instance variable" is defined within the class body with a ...
Class variables – belong to the class as a whole; there is only one copy of each variable, shared across all instances of the class; Instance variables or attributes – data that belongs to individual objects; every object has its own copy of each one. All 4 variables mentioned above (first_name, position etc) are instance variables. Member ...
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:
The virtual method table is the same for all objects belonging to the same class, and is therefore typically shared between them. Objects belonging to type-compatible classes (for example siblings in an inheritance hierarchy) will have virtual method tables with the same layout: the address of a given method will appear at the same offset for ...
[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]
Virtual inheritance is a C++ technique that ensures only one copy of a base class ' s member variables are inherited by grandchild derived classes. Without virtual inheritance, if two classes B and C inherit from a class A, and a class D inherits from both B and C, then D will contain two copies of A ' s member variables: one via B, and one via C.