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Python allows the creation of class methods and static methods via the use of the @classmethod and @staticmethod decorators. The first argument to a class method is the class object instead of the self-reference to the instance. A static method has no special first argument. Neither the instance, nor the class object is passed to a static method.
The curiously recurring template pattern (CRTP) is an idiom, originally in C++, in which a class X derives from a class template instantiation using X itself as a template argument. [1] More generally it is known as F-bound polymorphism , and it is a form of F -bounded quantification .
An example would be a static method to sum the values of all the variables of every instance of a class. For example, if there were a Product class it might have a static method to compute the average price of all products. A static method can be invoked even if no instances of the class exist yet.
C++ does not have the keyword super that a subclass can use in Java to invoke the superclass version of a method that it wants to override. Instead, the name of the parent or base class is used followed by the scope resolution operator. For example, the following code presents two classes, the base class Rectangle, and the derived class Box.
In ADO.NET, IDbCommand.CreateParameter is an example of the use of factory method to connect parallel class hierarchies. In Qt , QMainWindow::createPopupMenu Archived 2015-07-19 at the Wayback Machine is a factory method declared in a framework that can be overridden in application code .
Python has data classes which provides equality testing and can be made immutable using the frozen parameter. [21] It overrides the __str__ dunder method. [22] This example implementation includes a static method which can be used to initialize a new instance with a randomly generated universally unique identifier (UUID).
It is a form of method dispatch, which describes how a language or environment will select which implementation of a method or function to use. [ 1 ] Examples are templates in C++ , and generic programming in Fortran and other languages, in conjunction with function overloading (including operator overloading ).
[1] [2] An instance of a helper class is called a helper object (for example, in the delegation pattern). Helper classes are often created in introductory programming lessons, after the novice programmer has moved beyond creating one or two classes. A utility class is a special case of a helper class in which the methods are all static. [3]