const_iterator Class Reference
(QSet::const_iterator)
[QtCore module]

Detailed Description

The QSet::const_iterator class provides an STL-style const iterator for QSet.

QSet features both STL-style iterators and Java-style iterators. The STL-style iterators are more low-level and more cumbersome to use; on the other hand, they are slightly faster and, for developers who already know STL, have the advantage of familiarity.

QSet<Key, T>::const_iterator allows you to iterate over a QSet. If you want to modify the QSet as you iterate over it, you must use QSet::iterator instead. It is generally good practice to use QSet::const_iterator on a non-const QSet as well, unless you need to change the QSet through the iterator. Const iterators are slightly faster, and can improve code readability.

The default QSet::const_iterator constructor creates an uninitialized iterator. You must initialize it using a function like QSet::begin(), QSet::end(), or QSet::insert() before you can start iterating. Here's a typical loop that prints all the items stored in a set:

 QSet<QString> set;
 set << "January" << "February" << ... << "December";

 QSet<QString>::const_iterator i;
 for (i = set.begin(); i != set.end(); ++i)
     qDebug() << *i;

STL-style iterators can be used as arguments to generic algorithms. For example, here's how to find an item in the set using the qFind() algorithm:

 QSet<QString> set;
 ...
 QSet<QString>::iterator it = qFind(set.begin(), set.end(), "Jeanette");
 if (it != set.constEnd())
     cout << "Found Jeanette" << endl;

Multiple iterators can be used on the same set. However, you may not attempt to modify the container while iterating on it.

See also QSet::iterator and QSetIterator.

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