You do not have permission to edit this page, for the following reasons:

This IP address has been blocked from editing Wikipedia.
This does not affect your ability to read Wikipedia pages.
Most people who see this message have done nothing wrong. Some kinds of blocks restrict editing from specific service providers or telecom companies in response to recent abuse or vandalism, and can sometimes affect other users who are unrelated to that abuse. Review the information below for assistance if you do not believe that you have done anything wrong.

The IP address or range 3.92.0.0/16 has been blocked by ‪Blablubbs‬ for the following reason(s):

The IP address that you are currently using has been blocked because it is believed to be a web host provider or colocation provider. To prevent abuse, web hosts and colocation providers may be blocked from editing Wikipedia.
You will not be able to edit Wikipedia using a web host or colocation provider because it hides your IP address, much like a proxy or VPN.
We recommend that you attempt to use another connection to edit. For example, if you use a proxy or VPN to connect to the internet, turn it off when editing Wikipedia. If you edit using a mobile connection, try using a Wi-Fi connection, and vice versa. If you are using a corporate internet connection, switch to a different Wi-Fi network. If you have a Wikipedia account, please log in.
If you do not have any other way to edit Wikipedia, you will need to request an IP block exemption.

How to appeal if you are confident that your connection does not use a colocation provider's IP address:
If you are confident that you are not using a web host, you may appeal this block by adding the following text on your talk page: ((unblock|reason=Caught by a colocation web host block but this host or IP is not a web host. My IP address is _______. Place any further information here. ~~~~)). You must fill in the blank with your IP address for this block to be investigated. Your IP address can be determined here. Alternatively, if you wish to keep your IP address private you can use the unblock ticket request system. There are several reasons you might be editing using the IP address of a web host or colocation provider (such as if you are using VPN software or a business network); please use this method of appeal only if you think your IP address is in fact not a web host or colocation provider.

Administrators: The IP block exemption user right should only be applied to allow users to edit using web host in exceptional circumstances, and requests should usually be directed to the functionaries team via email. If you intend to give the IPBE user right, a CheckUser needs to take a look at the account. This can be requested most easily at SPI Quick Checkuser Requests. Unblocking an IP or IP range with this template is highly discouraged without at least contacting the blocking administrator.

This block will expire on 10:52, 20 August 2024. Your current IP address is 3.92.45.30.

Even when blocked, you will usually still be able to edit your user talk page, as well as email administrators and other editors.

For information on how to proceed, please read the FAQ for blocked users and the guideline on block appeals. The guide to appealing blocks may also be helpful.

Other useful links: Blocking policy · Help:I have been blocked
This IP address range has been globally blocked.
This does not affect your ability to read Wikipedia pages.
Most people who see this message have done nothing wrong. Some kinds of blocks restrict editing from specific service providers or telecom companies in response to recent abuse or vandalism, and can sometimes affect other users who are unrelated to that abuse. Review the information below for assistance if you do not believe that you have done anything wrong.

This block affects editing on all Wikimedia wikis.
The IP address or range 3.92.0.0/16 has been globally blocked by ‪Jon Kolbert‬ for the following reason(s):

Open proxy/Webhost: See the help page if you are affected

This block will expire on 05:35, 21 February 2029. Your current IP address is 3.92.45.30.

Even while globally blocked, you will usually still be able to edit pages on Meta-Wiki.

If you believe you were blocked by mistake, you can find additional information and instructions in the No open proxies global policy. Otherwise, to discuss the block please post a request for review on Meta-Wiki. You could also send an email to the stewards VRT queue at stewards@wikimedia.org including all above details.

Other useful links: Global blocks · Help:I have been blocked

You can view and copy the source of this page:

((Short description|Style of object-oriented programming where inheritance is based on classes))
((Refimprove|date=February 2013))

'''Class-based programming''', or more commonly '''class-orientation''', is a style of [[object-oriented programming]] (OOP) in which [[inheritance (object-oriented programming)|inheritance]] occurs via defining ''[[class (computer programming)|class]]es'' of [[object (computer science)|object]]s, instead of inheritance occurring via the objects alone (compare [[prototype-based programming]]).

The most popular and developed model of OOP is a class-based model, instead of an object-based model. In this model, objects are entities that combine ''[[state (computer science)|state]]'' (i.e., data), ''[[behavior]]'' (i.e., procedures, or ''[[method (computer science)|method]]s'') and ''[[identity (object-oriented programming)|identity]]'' (unique existence among all other objects). The structure and behavior of an object are defined by a [[class (object-oriented programming)|class]], which is a [[definition]], or [[blueprint]], of all objects of a specific type. An object must be explicitly created based on a class and an object thus created is considered to be an [[instantiation (computer science)|instance]] of that class. An object is similar to a [[data structure|structure]], with the addition of method pointers, member access control, and an implicit data member which locates instances of the class (i.e., objects of the class) in the class hierarchy (essential for runtime inheritance features).

==Encapsulation==
[[Information hiding|Encapsulation]] prevents users from breaking the [[Invariant (computer science)|invariants]] of the class, which is useful because it allows the implementation of a class of objects to be changed for aspects not exposed in the interface without impact to user code. The definitions of encapsulation focus on the grouping and packaging of related information ([[cohesion (computer science)|cohesion]]) rather than security issues.

==Inheritance==
((Main|Inheritance (object-oriented programming)|l1=Inheritance))

In class-based programming, [[inheritance (object-oriented programming)|inheritance]] is done by defining new classes as [[Extension (semantics)|extensions]] of existing classes: the existing class is the [[parent class]] and the new class is the [[Subclass (computer science)|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 ''[[multiple inheritance]].'' This organizes classes into a [[hierarchy]], either a ''[[Tree (set theory)|tree]]'' (if single inheritance) or ''[[Lattice (order)|lattice]]'' (if multiple inheritance).

The defining feature of inheritance is that both interface and implementation are inherited; if only interface is inherited, this is known as [[interface inheritance]] or ''subtyping.'' Inheritance can also be done without classes, as in [[prototype-based programming]].

==Critique==
Class-based languages, or, to be more precise, [[typed language]]s, where [[Subclass (computer science)|subclassing]] is the only way of [[subtyping]], have been criticized for mixing up implementations and interfaces&mdash;the essential principle in object-oriented programming. The critics say one might create a bag class that stores a [[Collection class|collection]] of objects, then extend it to make a new class called a set class where the duplication of objects is eliminated.<ref>((cite web|first=Oleg|last=Kiselyov|title=Subtyping, Subclassing, and Trouble with OOP|url=http://okmij.org/ftp/Computation/Subtyping/|access-date=7 October 2012))</ref><ref>((cite web|title=A set cannot be a subtype of a bag|last=Ducasse|first=Stéphane|url=http://stephane.ducasse.free.fr/Resources/LecturesInPowerpoint/STOOP-416-LSP.ppt|access-date=7 October 2012))</ref>  Now, a function that takes an object of the bag class may expect that adding two objects increases the size of a bag by two, yet if one passes an object of a set class, then adding two objects may or may not increase the size of a bag by two. The problem arises precisely because subclassing implies subtyping even in the instances where the principle of subtyping, known as the [[Liskov substitution principle]], does not hold. [[Barbara Liskov]] and [[Jeannette Wing]] formulated the principle succinctly in a 1994 paper as follows:
<!-- inline math as LaTeX has poor baseline alignment (better with MathJaX HTML/CSS rendering of LaTeX)     
:''Let <math>q(x)</math> be a property provable about objects <math>x</math> of type <math>T</math>. Then <math>q(y)</math> should be provable for objects <math>y</math> of type <math>S</math>, where <math>S</math> is a subtype of <math>T</math>.''
--><!-- inline math as HTML --> 
<blockquote>''Subtype Requirement'': Let ((tmath| \phi(x) )) be a property provable about objects ((tmath| x )) of type ((tmath| T)).  Then ((tmath| \phi(y) )) should be true for objects ((tmath| y )) of type ((tmath| S )) where ((tmath| S )) is a subtype of ((tmath| T)). </blockquote>
<!-- inline math as HTML bold
:''Let ((math| '''q(x)''' )) be a property provable about objects ((math| '''x''' )) of type ((math| '''T'''. )) Then ((math| '''q(y)''' )) should be provable for objects ((math| '''y''' )) of type ((math| '''S''', )) where ((math| '''S''' )) is a subtype of ((math| '''T'''. ))''
 -->
Thus, normally one must distinguish subtyping and subclassing. Most current object-oriented languages distinguish subtyping and subclassing, however some approaches to design do not.

Also, another common example is that a person object created from a [[Subclass (computer science)|child class]] cannot become an object of [[parent class]] because a child class and a parent class inherit a person class but class-based languages mostly do not allow to change the kind of class of the object at runtime. For class-based languages, this restriction is essential in order to preserve unified view of the class to its users. The users should not need to care whether one of the implementations of a method happens to cause changes that break the [[Invariant (computer science)|invariants]] of the class. Such changes can be made by destroying the object and constructing another in its place. Polymorphism can be used to preserve the relevant interfaces even when such changes are done, because the objects are viewed as black box abstractions and accessed via object [[identity (object-oriented programming)|identity]]. However, usually the value of object references referring to the object is changed, which causes effects to client code.

==Example languages==
((Category see also|Class-based programming languages))
Although [[Simula]] introduced the class abstraction, the canonical example of a class-based language is [[Smalltalk]]. Others include [[PHP]], [[C++]], [[Java (programming language)|Java]], [[C Sharp (programming language)|C#]], and [[Objective-C]].

==See also==
*[[Prototype-based programming]] (contrast)
*[[Programming paradigm]]s
*[[Class (computer programming)]]

==References==
((Reflist))

((Programming paradigms navbox))
((Types of programming languages))

((DEFAULTSORT:Class-Based Programming))
[[Category:Object-oriented programming]]

Pages transcluded onto the current version of this page (help):

Class-based programming (edit)
Template:Ambox (view source) (template editor protected)
Template:Category see also (view source) (template editor protected)
Template:Category see also/Category pair check (view source) (template editor protected)
Template:Cite web (view source) (protected)
Template:Find sources mainspace (view source) (template editor protected)
Template:Hlist/styles.css (view source) (protected)
Template:Main (view source) (template editor protected)
Template:Main other (view source) (protected)
Template:More citations needed (view source) (template editor protected)
Template:Navbox (view source) (template editor protected)
Template:Pagetype (view source) (protected)
Template:Programming paradigms navbox (edit)
Template:Refimprove (view source) (template editor protected)
Template:Reflist (view source) (protected)
Template:Reflist/styles.css (view source) (protected)
Template:SDcat (view source) (protected)
Template:Short description (view source) (protected)
Template:Short description/lowercasecheck (view source) (protected)
Template:Tmath (view source) (semi-protected)
Template:Types of programming languages (edit)
Module:Arguments (view source) (protected)
Module:Category handler (view source) (protected)
Module:Category handler/blacklist (view source) (protected)
Module:Category handler/config (view source) (protected)
Module:Category handler/data (view source) (protected)
Module:Category handler/shared (view source) (protected)
Module:Category see also (view source) (template editor protected)
Module:Check for unknown parameters (view source) (protected)
Module:Citation/CS1 (view source) (protected)
Module:Citation/CS1/COinS (view source) (protected)
Module:Citation/CS1/Configuration (view source) (protected)
Module:Citation/CS1/Date validation (view source) (protected)
Module:Citation/CS1/Identifiers (view source) (protected)
Module:Citation/CS1/Utilities (view source) (protected)
Module:Citation/CS1/Whitelist (view source) (protected)
Module:Citation/CS1/styles.css (view source) (protected)
Module:Disambiguation/templates (view source) (protected)
Module:Find sources (view source) (template editor protected)
Module:Find sources/config (view source) (template editor protected)
Module:Find sources/links (view source) (template editor protected)
Module:Find sources/templates/Find sources mainspace (view source) (template editor protected)
Module:Format link (view source) (template editor protected)
Module:Hatnote (view source) (template editor protected)
Module:Hatnote/styles.css (view source) (template editor protected)
Module:Hatnote list (view source) (template editor protected)
Module:Labelled list hatnote (view source) (template editor protected)
Module:Message box (view source) (protected)
Module:Message box/ambox.css (view source) (protected)
Module:Message box/configuration (view source) (protected)
Module:Namespace detect/config (view source) (protected)
Module:Namespace detect/data (view source) (protected)
Module:Navbar (view source) (protected)
Module:Navbar/configuration (view source) (protected)
Module:Navbar/styles.css (view source) (protected)
Module:Navbox (view source) (template editor protected)
Module:Navbox/configuration (view source) (template editor protected)
Module:Navbox/styles.css (view source) (template editor protected)
Module:Pagetype (view source) (protected)
Module:Pagetype/config (view source) (protected)
Module:Pagetype/disambiguation (view source) (protected)
Module:Pagetype/rfd (view source) (template editor protected)
Module:Pagetype/setindex (view source) (protected)
Module:Pagetype/softredirect (view source) (protected)
Module:SDcat (view source) (protected)
Module:String (view source) (protected)
Module:Unsubst (view source) (protected)
Module:Wikitext Parsing (view source) (protected)
Module:Yesno (view source) (protected)

Return to Class-based programming.

Retrieved from "https://en.wikipedia.org/wiki/Class-based_programming"