Top Qs
Timeline
Chat
Perspective
Interface (object-oriented programming)
Abstraction of a class From Wikipedia, the free encyclopedia
Remove ads
In object-oriented programming, an interface or protocol type[a] 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.[1] A class which provides the methods listed in an interface is said to implement the interface,[1] or to adopt the protocol.[2]
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 (except that two of these objects can be compared via compareTo()
).
Remove ads
Examples
Summarize
Perspective
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 {
void fly();
}
interface Vocal {
void vocalize();
}
public class Bird extends Theropod implements Flyable, Vocal {
// ...
public void fly() { ... }
public void vocalize() { ... }
}
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.[3] Classes may also explicitly subclass an ABC, such as collections.abc.Iterable
.
Type classes in languages like Haskell, or module signatures in ML and OCaml, are used for many of the same things as are interfaces.[clarification needed]
In Rust, interfaces are called traits.[4] In Rust, a struct
does not contain methods, but may add methods through separate impl
blocks:
trait Speak {
fn speak(&self);
}
struct Dog {
// Structs only contain their fields
name: String
}
impl Dog {
// Not from a trait
fn new(name: String) -> Self {
Dog { name }
}
}
impl Speak for Dog {
// From a trait
fn speak(&self) {
println!("{} says 'Woof!'", self.name);
}
}
fn main() {
let dog = Dog::new("Arlo".to_string());
dog.speak();
}
Remove ads
See also
Notes
- Use of these terms varies by programming language. Java and languages derived from it tend to use interface, while protocol is generally more popular elsewhere.
References
Wikiwand - on
Seamless Wikipedia browsing. On steroids.
Remove ads