The Tulip Container Classes

Examples

The first group of examples show how to use the new Java-style iterators. The main difference between the Java-style iterators and the STL-style iterators is that the Java-style ones point between items (or before the first item, or after the last item), whereas the STL ones point at an item (or past the last item). One advantage of the Java-style iterators is that iterating forward and backward are symmetric operations.

Traversing a container using a Java-style iterator:

 // forward                                  // backward
 QList<QString> list;                        QList<QString> list;
 ...                                         ...
 QListIterator<QString> i(list);             QListIterator<QString> i(list);
 while (i.hasNext())                         i.toBack();
     cout << i.next().ascii() << endl;       while (i.hasPrev())
                                                 cout << i.prev().ascii() << endl;

Modifying items using a Java-style iterator:

 // forward                                  // backward
 QMutableListIterator<int> i(list);          QMutableListIterator<int> i(list);
 while (i.hasNext())                         i.toBack();
     if (i.next() > 128)                     while (i.hasPrev())
         i.setValue(128);                        if (i.prev() > 128)
                                                     i.setValue(128);

Removing items using a Java-style iterator:

 // forward                                  // backward
 QMutableListIterator<int> i(list);          QMutableListIterator<int> i(list);
 while (i.hasNext())                         i.toBack();
     if (i.next() % 2 != 0)                  while (i.hasPrev())
         i.remove();                             if (i.prev() % 2 != 0)
                                                     i.remove();

Iterating over items with a particular value using STL-style vs. Java-style iterators:

 // STL-style                                // Java-style
 QMap<int, QWidget *>::const_iterator i;     QMapIterator<int, QWidget *> i(map);
 for (i = map.begin(); i != map.end(); ++i)  while (i.findNext(widget))
     if (i.value() == widget)                    cout << "Found widget " << widget
         cout << "Found widget " << widget            << " under key "
              << " under key "                        << i.key() << endl;
              << i.key() << endl;

Modifying and removing items using STL-style vs. Java-style iterators:

 // STL-style                                // Java-style
 QList<int>::iterator i = list.begin();      QMutableListIterator<int> i(list);
 while (i != list.end()) {                   while (i.hasNext()) {
     if (*i == 0) {                              int val = i.next();
         i = list.erase(i);                      if (val < 0)
     } else {                                        i.setValue(-val);
         if (*i < 0)                             else if (val == 0)
             *i = -*i;                               i.remove();
         ++i;                                }
     }
 }

The next group of examples show the API of the container classes themselves. The API is similar to the QTL classes of Qt 3, but is nicer in many respects.

Iterating over a QList using an index (which is fast even for large lists, because QList is implemented as an array-list):

 QList<double> list;
 ...
 for (int i = 0; i < list.size(); ++i) {
     if (list[i] < 0.0)
         list[i] = 0.0;
 }

Retrieving a value from a map, using a default value if the key doesn't exist:

 QMap<QString, int> map;
 ...
 map.value("TIMEOUT", 30);  // returns 30 if "TIMEOUT" isn't in the map

Getting all the values for a particular key in a QMultiMap or QMultiHash:

 QMultiMap<QString, int> map;
 ...
 QList<int> values = map.values("TIMEOUT");