4.2. Iterators

4.2. Iterators
	Chapter 4. Lists

[ fromfile: iterators.xml id: iterators ]

An iterator is an object that provides indirect access to each element in a container.
It is specifically designed to be used in a loop.

Qt supports the following styles of iteration:
- Qt style foreach loops, similar to Perl and Python
- Java 1.2 style Iterator, which always points between elements
- Standard Library style ContainerType::iterator
- Hand-made while or for loops that use the getters of the container
- QDirIterator, for iterating through entries in a directory structure

The Iterator Pattern

A class, function, or programming element that provides a generic way to access elements of a collection sequentially without being type-restricted is an implementation of the Iterator design pattern. ^[23] C++ iterators, Java-style Iterators, and foreach loops are all examples of the Iterator pattern.

There are many classes in Qt that provide specialized iteration for various types of data, such as QDirIterator, QSortFilterProxyModel, QTreeWidgetItemIterator, and QDomNodeList.
When an iterator is introduced, its definition must contain enough information to enable it to move from one item to the next in the container.

^[23]We discuss design patterns in more detail in Section 7.4.


4.1. Introduction to Containers		4.2.1. `QStringList` and iteration