====== Interface ======

===== Meaning 1: Interface as a Concept =====

==== Alternative Terms ====
/*i.e. alternative names meaning the same thing*/

==== Definition ====
An **interface** defines the interaction between certain [[modules]].

==== Description ====
Interface is a very general concept which refers to the interaction points of arbitrary modules:
  * The interface of a [[class]] is defined by its public [[methods]].
  * The interface of a method is defined by its [[method signature]].
  * The interface of a subsystem is defined by the public ([[patterns:facade]]) classes.
  * The interface of a network service is defined by a [[protocol]].
  * The interface of a hardware component is defined by pins, wires, signals, protocols, etc.
  * A [[graphical user interface]] is defined by buttons, menus, text boxes, and other controls.

The interface defines how a module shall be used. There may be ways circumventing the interface and accessing internal parts of a module directly. This should be avoided ([[principels:Information Hiding/Encapsulation|IH/E]]) but is sometimes done. 

A module can be described as having a [[provided interface]] and a [[required interface]].

==== Examples ====


==== Alternative Definitions ====
/*i.e. slightly different definitions for basically the same thing*/

==== See Also ====
  * [[Module]]
  * [[Application Programming Interface]] (API)
  * [[Application Binary Interface]] (ABI)
  * [[Service Provider Interface]] (SPI)

==== Further Reading ====
  * [[wp>Interface (computing)]]


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===== Meaning 2: Interface as a Language Construct =====

==== Alternative Terms ====
/*i.e. alternative names meaning the same thing*/

==== Definition ====
An **''interface''** is a [[language construct]] of certain [[object-oriented programming languages]] resembling an [[abstract class]] without any implementation.

==== Description ====
An ''interface'' is similar to a [[class]] but does not contain any attributes or implementations---just method signatures. Typically object-oriented programming languages use ''interfaces'' in order to avoid the problems of [[multiple inheritance]], especially the [[diamond problem]]. In such languages a class can inherit from only one class but multiple interfaces. In that way there is only one implementation inherited.

There are ''interfaces'' in Java, C#, Object Pascal/Delphi and possibly also in other languages.

Note that in this wiki whenever the language construct is meant (and not the concept) ''interface'' shall be written using a monospace font: ''interface'' vs. interface.

==== Examples ====
[[http://docs.oracle.com/javase/7/docs/api/|java.util.Collection<E>]]:
<code java>
public interface Collection<E> extends Iterable<E> 
{
    boolean add(E e);
    boolean addAll(Collection<? extends E> c)
    void clear()
    boolean contains(Object o)
    ...
}
</code>
==== Alternative Definitions ====
/*i.e. slightly different definitions for basically the same thing*/

==== See Also ====
  * [[Class]]
  * [[Abstract Class]]
  * [[Mixin]]

==== Further Reading ====


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===== Other Meanings =====
/*i.e. the same term referring to something different; put short mentions here or better add more detailed descriptions as additional sections */

  * In [[Object Pascal]] a [[unit]], i.e. a pas-file, typically contains an interface and an implementation section. The interface section lists the declarations which are visible outside the unit.

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===== Discussion =====

Discuss this wiki article and the term on the corresponding [[talk:glossary:Interface|talk page]].