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Reportedly, Java inventor James Gosling has spoken against implementation inheritance, stating that he would not include it if he were to redesign Java. [19] Language designs that decouple inheritance from subtyping (interface inheritance) appeared as early as 1990; [ 21 ] a modern example of this is the Go programming language.
Inheritance is not obvious in Wirth's design since his nomenclature looks in the opposite direction: It is called type extension and the viewpoint is from the parent down to the inheritor. Many programming languages that existed before OOP have added object-oriented features, including Ada , BASIC , Fortran , Pascal , and COBOL .
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]
In prototype-based languages that use delegation, the language runtime is capable of dispatching the correct method or finding the right piece of data simply by following a series of delegation pointers (from object to its prototype) until a match is found.
On the other hand, inheritance can be statically type-checked, while delegation generally cannot without generics (although a restricted version of delegation can be statically typesafe [7]). Delegation can be termed "run-time inheritance for specific objects." Here is a pseudocode example in a C#/Java like language:
Not all languages support multiple inheritance. For example, Java allows a class to implement multiple interfaces, but only inherit from one class. [22] If multiple inheritance is allowed, the hierarchy is a directed acyclic graph (or DAG for short), otherwise it is a tree. The hierarchy has classes as nodes and inheritance relationships as links.
Chapter 1 is a discussion of object-oriented design techniques, based on the authors' experience, which they believe would lead to good object-oriented software design, including: "Program to an interface, not an implementation." (Gang of Four 1995:18) Composition over inheritance: "Favor 'object composition' over 'class inheritance'." (Gang of ...
In object-oriented programming, the open–closed principle (OCP) states "software entities (classes, modules, functions, etc.) should be open for extension, but closed for modification"; [1] that is, such an entity can allow its behaviour to be extended without modifying its source code. The name open–closed principle has been used in two ways.