Object-oriented programming: Difference between revisions

Revision as of 20:38, 27 May 2023

Revision as of 06:48, 9 June 2023

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| year = 2011 | pages = 313–343}}</ref><ref>{{Cite book|last1=Lewis|first1=John|last2=Loftus|first2= William|title=Java Software Solutions Foundations of Programming Design 6th ed|publisher=Pearson Education Inc.|year=2008|isbn=978-0-321-53205-3}}, section 1.6 "Object-Oriented Programming"</ref> OOP languages are diverse, but the most popular ones are [[Class-based programming|class-based]], meaning that objects are [[instance (computer science)|instances]] of [[class (computer science)|classes]], which also determine their [[data type|types]].

Many of the most widely used programming languages (such as C++, Java{{sfn|Bloch|2018|loc=Foreword|pp=xi-xii}}, Python, etc.) are [[multi-paradigm programming language|multi-paradigm]] and they support object-oriented programming to a greater or lesser degree, typically in combination with [[imperative programming|imperative]], [[procedural programming]].

Significant object-oriented languages include: [[Ada (programming language)|Ada]], [[ActionScript]], [[C++]], [[Common Lisp]], [[C Sharp (programming language)|C#]], [[Dart (programming language)|Dart]], [[Eiffel (programming language)|Eiffel]], [[Fortran|Fortran 2003]], [[Haxe]], [[Java (programming language)|Java]]{{sfn|Bloch|2018|loc=Foreword|pp=xi-xii}}, [[JavaScript]], [[Kotlin (programming language)|Kotlin]], [[Logo (programming language)|logo]], [[MATLAB]], [[Objective-C]], [[Object Pascal]], [[Perl]], [[PHP]], [[Python (programming language)|Python]], [[R (programming language)|R]], [[Raku (programming language)|Raku]], [[Ruby (programming language)|Ruby]], [[Scala (programming language)|Scala]], [[SIMSCRIPT]], [[Simula]], [[Smalltalk]], [[Swift (programming language)|Swift]], [[Vala (programming language)|Vala]] and [[Visual Basic.NET]].

==History==

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Data abstraction is a design pattern in which data are visible only to semantically related functions, so as to prevent misuse. The success of data abstraction leads to frequent incorporation of [[Information hiding|data hiding]] as a design principle in object oriented and pure functional programming.

If a class does not allow calling code to access internal object data and permits access through methods only, this is a form of information hiding known as [[Abstraction (computer science)|abstraction]]. Some languages (Java, for example) let classes enforce access restrictions explicitly, for example denoting internal data with the <code>private</code> keyword and designating methods intended for use by code outside the class with the <code>public</code> keyword.{{sfn|Bloch|2018|loc=Chapter §4 Item15 Minimize the accessibility of classes and members|pp=73-77}} Methods may also be designed public, private, or intermediate levels such as <code>protected</code> (which allows access from the same class and its subclasses, but not objects of a different class).{{sfn|Bloch|2018|loc=Chapter §4 Item15 Minimize the accessibility of classes and members|pp=73-77}} In other languages (like Python) this is enforced only by convention (for example, <code>private</code> methods may have names that start with an [[underscore]]). In C#, Swift & Kotlin languages, <code>internal</code> keyword permits access only to files present in same assembly, package or module as that of the class.<ref>{{Cite web |date=2023-01-05 |title=What is Object Oriented Programming (OOP) In Simple Words? – Software Geek Bytes |url=https://softwaregeekbytes.com/object-oriented-programming-simple-words/ |access-date=2023-01-17 |language=en-US}}</ref>

===Encapsulation===

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Subclasses can override the methods defined by superclasses. [[Multiple inheritance]] is allowed in some languages, though this can make resolving overrides complicated. Some languages have special support for [[mixin]]s, though in any language with multiple inheritance, a mixin is simply a class that does not represent an is-a-type-of relationship. Mixins are typically used to add the same methods to multiple classes. For example, class UnicodeConversionMixin might provide a method unicode_to_ascii() when included in class FileReader and class WebPageScraper, which don't share a common parent.

[[Abstract class]]es cannot be instantiated into objects; they exist only for the purpose of inheritance into other "concrete" classes that can be instantiated. In Java, the <code>[[final (Java)|final]]</code> keyword can be used to prevent a class from being subclassed.{{sfn|Bloch|2018|loc=Chapter §2 Item 4 Enforce noninstantiability with a private constructor|p=19}}

The doctrine of [[composition over inheritance]] advocates implementing has-a relationships using composition instead of inheritance. For example, instead of inheriting from class Person, class Employee could give each Employee object an internal Person object, which it then has the opportunity to hide from external code even if class Person has many public attributes or methods. Some languages, like [[Go (programming language)|Go]] do not support inheritance at all.

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|doi = 10.1145/1113034.1113040

|s2cid = 11485502

}}

*{{cite book

| title= "Effective Java: Programming Language Guide"

|last=Bloch

| first=Joshua

| publisher=Addison-Wesley

| edition=third

| isbn=978-0134685991

| year=2018

}}

* {{Cite book