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For example, the decorator pattern (as mentioned above) has been proposed to overcome the static nature of inheritance between classes. As a more fundamental solution to the same problem, role-oriented programming introduces a distinct relationship, played-by, combining properties of inheritance and composition into a new concept. [citation needed]
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]
The decoration features (e.g., methods, properties, or other members) are usually defined by an interface, mixin (a.k.a. trait) or class inheritance which is shared by the decorators and the decorated object. In the previous example, the class Component is inherited by both the ConcreteComponent and the subclasses that descend from Decorator.
In C#, class methods, indexers, properties and events can all be overridden. Non-virtual or static methods cannot be overridden. The overridden base method must be virtual, abstract, or override. In addition to the modifiers that are used for method overriding, C# allows the hiding of an inherited property or method.
The factory method design pattern solves problems such as: How can an object's subclasses redefine its subsequent and distinct implementation? The pattern involves creation of a factory method within the superclass that defers the object's creation to a subclass's factory method.
In a language that supports inheritance, an abstract class, or abstract base class (ABC), is a class that cannot be directly instantiated. By contrast, a concrete class is a class that can be directly instantiated. Instantiation of an abstract class can occur only indirectly, via a concrete subclass.
Classes may inherit from other classes, creating a hierarchy of "subclasses". For example, an "Employee" class might inherit from a "Person" class. This means the Employee object will have all the variables from Person (like name variables) plus any new variables (like job position and salary).
A sample UML class and sequence diagram for the Bridge design pattern. [3]In the above Unified Modeling Language class diagram, an abstraction (Abstraction) is not implemented as usual in a single inheritance hierarchy.