Iterator pattern

Iterator pattern

In object-oriented programming, the iterator pattern is a design pattern in which an iterator is used to traverse a container and access the container's elements. The iterator pattern decouples algorithms from containers; in some cases, algorithms are necessarily container-specific and thus cannot be decoupled.

For example, the hypothetical algorithm SearchForElement can be implemented generally using a specified type of iterator rather than implementing it as a container-specific algorithm. This allows SearchForElement to be used on any container which supports the required type of iterator.

Contents

Definition

The essence of the Iterator Factory method Pattern is to "Provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation.".[1]

Language-specific implementation

Some languages standardize syntax. C++ and Python are notable examples.

C++

C++ implements iterators with the semantics of pointers in that language. In C++, a class can overload all of the pointer operations, so an iterator can be implemented that acts more or less like a pointer, complete with dereference, increment, and decrement. This has the advantage that C++ algorithms such as std::sort can immediately be applied to plain old memory buffers, and that there is no new syntax to learn. However, it requires an "end" iterator to test for equality, rather than allowing an iterator to know that it has reached the end. In C++ language, we say that an iterator models the iterator concept.

Python

Python prescribes a syntax for iterators as part of the language itself, so that language keywords such as for work with what Python calls sequences. A sequence has an __iter__() method that returns an iterator object. The "iterator protocol" which requires next() return the next element or raise a StopIteration exception upon reaching the end of the sequence. Iterators also provide an __iter__() method returning themselves so that they can also be iterated over e.g., using a for loop. (In Python 3, next() was replaced with __next__().)[2]

Java

Java has an Iterator interface that the Collections should implement in order to transverse the elements of the collection

See also

References

External links



Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать курсовую

Look at other dictionaries:

  • Iterator — In computer science, an iterator is an object which allows a programmer to traverse through all the elements of a collection, regardless of its specific implementation. An iterator is sometimes called a cursor, especially within the context of a… …   Wikipedia

  • Iterator — Itérateur (patron de conception) En génie logiciel, l itérateur est un patron de conception (design pattern) comportemental. Un itérateur est un objet qui permet de parcourir tous les éléments contenus dans un autre objet, le plus souvent un… …   Wikipédia en Français

  • Design Pattern — Patron de conception Pour les articles homonymes, voir Patron. Un patron de conception (design pattern en anglais) est un concept de génie logiciel destiné à résoudre les problèmes récurrents suivant le paradigme objet. En français on utilise… …   Wikipédia en Français

  • Design pattern — Patron de conception Pour les articles homonymes, voir Patron. Un patron de conception (design pattern en anglais) est un concept de génie logiciel destiné à résoudre les problèmes récurrents suivant le paradigme objet. En français on utilise… …   Wikipédia en Français

  • Behavioral pattern — In software engineering, behavioral design patterns are design patterns that identify common communication patterns between objects and realize these patterns. By doing so, these patterns increase flexibility in carrying out this communication.… …   Wikipedia

  • Multiton pattern — In software engineering, the multiton pattern is a design pattern similar to the singleton, which allows only one instance of a class to be created. The multiton pattern expands on the singleton concept to manage a map of named instances as key… …   Wikipedia

  • Software design pattern — In software engineering, a design pattern is a general reusable solution to a commonly occurring problem within a given context in software design. A design pattern is not a finished design that can be transformed directly into code. It is a… …   Wikipedia

  • Visitor pattern — [ LePUS3 ( [http://lepus.org.uk/ref/legend/legend.xml legend] ) ] In object oriented programming and software engineering, the visitor design pattern is a way of separating an algorithm from an object structure upon which it operates. A practical …   Wikipedia

  • Singleton Pattern — Das Singleton (auch Einzelstück genannt) ist ein in der Softwareentwicklung eingesetztes Entwurfsmuster und gehört zur Kategorie der Erzeugungsmuster (engl. Creational Patterns). Es verhindert, dass von einer Klasse mehr als ein Objekt erzeugt… …   Deutsch Wikipedia

  • Design Pattern — Entwurfsmuster (engl. design pattern) sind bewährte Lösungs Schablonen für wiederkehrende Entwurfsprobleme der Softwarearchitektur und Softwareentwicklung. Sie stellen damit eine wiederverwendbare Vorlage zur Problemlösung dar, die in einem… …   Deutsch Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”