QVectorIterator Class Reference
[QtCore module]

Detailed Description

The QVectorIterator class provides a Java-style const iterator for QVector and QStack.

QVector has both Java-style iterators and STL-style iterators. The Java-style iterators are more high-level and easier to use than the STL-style iterators; on the other hand, they are slightly less efficient.

An alternative to using iterators is to use index positions. Most QVector member functions take an index as their first parameter, making it possible to access, insert, and remove items without using iterators.

QVectorIterator<T> allows you to iterate over a QVector<T> (or a QStack<T>). If you want to modify the vector as you iterate over it, use QMutableVectorIterator<T> instead.

The QVectorIterator constructor takes a QVector as argument. After construction, the iterator is located at the very beginning of the vector (before the first item). Here's how to iterate over all the elements sequentially:

 QVector<float> vector;
 ...
 QVectorIterator<float> i(vector);
 while (i.hasNext())
     qDebug() << i.next();

The next() function returns the next item in the vector and advances the iterator. Unlike STL-style iterators, Java-style iterators point between items rather than directly at items. The first call to next() advances the iterator to the position between the first and second item, and returns the first item; the second call to next() advances the iterator to the position between the second and third item, returning the second item; and so on.

Here's how to iterate over the elements in reverse order:

 QVectorIterator<float> i(vector);
 i.toBack();
 while (i.hasPrevious())
     qDebug() << i.previous();

If you want to find all occurrences of a particular value, use findNext() or findPrevious() in a loop.

Multiple iterators can be used on the same vector. If the vector is modified while a QVectorIterator is active, the QVectorIterator will continue iterating over the original vector, ignoring the modified copy.

See also QMutableVectorIterator and QVector::const_iterator.

Member Function Documentation