Interface (object-oriented programming)

Template:Short description In object-oriented programming, an interface or protocol typeTemplate:Efn is a data type that acts as an abstraction of a class. It describes a set of method signatures, the implementations of which may be provided by multiple classes that are otherwise not necessarily related to each other.<ref name="csharp-learn">Template:Cite web</ref> A class which provides the methods listed in an interface is said to implement the interface,<ref name="csharp-learn" /> or to adopt the protocol.<ref name="swift-24h">Template:Cite book</ref>

If objects are fully encapsulated then the interface is the only way in which they may be accessed by other objects. For example, in Java, the Comparable interface specifies a method compareTo() which implementing classes must implement. This means that a sorting method, for example, can sort a collection of any objects of types which implement the Comparable interface, without having to know anything about the inner nature of the class (except that two of these objects can be compared by means of compareTo()).

Some programming languages provide explicit language support for interfaces: Ada, C#, D, Dart, Delphi, Go, Java, Logtalk, Object Pascal, Objective-C, OCaml, PHP, Racket, Seed7, Swift, Python 3.8. In languages supporting multiple inheritance, such as C++, interfaces are implemented as abstract classes.

In languages without explicit support, interfaces are often still present as conventions; this is known as duck typing. For example, in Python, any class can implement an __iter__ method and be used as a collection.<ref name="python-iter">Template:Cite web</ref>

Type classes in languages like Haskell, or module signatures in ML and OCaml, are used for many of the things that interfaces are used for.Template:Clarify

In Rust, interfaces are called traits.<ref>Template:Cite web</ref>

See also

• Concept (generic programming)
• Delegation (programming)
• Protocols in Objective-C
• Class (computer science)
• Encapsulation (computer science)
• Public interface
• Interface (Java)
• Application programming interface
• Interface (computing)
• List of basic computer science topics

References

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