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The modified object is often a class, a prototype, or a type. Extension methods are features of some object-oriented programming languages. There is no syntactic difference between calling an extension method and calling a method declared in the type definition. [1] Not all languages implement extension methods in an equally safe manner, however.
Composition over inheritance (or composite reuse principle) in object-oriented programming (OOP) is the principle that classes should favor polymorphic behavior and code reuse by their composition (by containing instances of other classes that implement the desired functionality) over inheritance from a base or parent class. [2]
public class Fruit {} // parent class public class Apple extends Fruit {} // child class public static void main (String [] args) {// The following is an implicit upcast: Fruit parent = new Apple (); // The following is a downcast. Here, it works since the variable `parent` is // holding an instance of Apple: Apple child = (Apple) parent;}
Decorator UML class diagram. The decorator pattern can be used to extend (decorate) the functionality of a certain object statically, or in some cases at run-time, independently of other instances of the same class, provided some groundwork is done at design time.
If a trait requires the consuming class to provide certain methods, the trait cannot know if those methods are semantically equivalent to the trait's needs. For some dynamic languages, such as Perl, the required method can only be identified by a method name, not a full method signature, making it harder to guarantee that the required method is appropriate.
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] Other languages, notably Java and C#, support a variant of abstract classes called an interface via a keyword in the language.
In class-based programming, inheritance is done by defining new classes as extensions of existing classes: the existing class is the parent class and the new class is the child class. If a child class has only one parent class, this is known as single inheritance , while if a child class can have more than one parent class, this is known as ...
Plain Old CLR Object is a play on the term plain old Java object from the Java EE programming world, which was coined by Martin Fowler in 2000. [2] POCO is often expanded to plain old C# object, though POCOs can be created with any language targeting the CLR.