Interface (object-oriented programming)
In object-oriented programming, an interface or protocol type 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. A class which provides the methods listed in an interface is said to implement the interface, or to adopt the protocol.
Interfaces are useful for encapsulation and reducing coupling. For example, in Java, the
Comparable interface specifies the method compareTo. Thus, a sorting method only needs to take objects of types which implement Comparable to sort them, without knowing about the inner nature of the class.Examples
Some programming languages provide explicit language support for interfaces: Ada, C#, D, Dart, Delphi, Go, Java, Logtalk, Object Pascal, Objective-C, OCaml, PHP, Racket, Swift, Python 3.8. In languages supporting multiple inheritance, such as C++, interfaces are abstract classes.In Java, an implementation of interfaces may look like:
class Animal
class Theropod extends Animal
interface Flyable
interface Vocal
public class Bird extends Theropod implements Flyable, Vocal
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 an iterable. Classes may also explicitly subclass an ABC, such as.Type classes in languages like Haskell, or module signatures in ML and OCaml, are used for many of the same things as are interfaces.
In Rust, interfaces are called traits. In Rust, a
struct does not contain methods, but may add methods through separate blocks:trait Pet
struct Dog
impl Dog
impl Pet for Dog
fn main