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diff --git a/doc/src/porting/qt4-tulip.qdoc b/doc/src/porting/qt4-tulip.qdoc new file mode 100644 index 0000000..5d818b0 --- /dev/null +++ b/doc/src/porting/qt4-tulip.qdoc @@ -0,0 +1,200 @@ +/**************************************************************************** +** +** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies). +** Contact: Nokia Corporation (qt-info@nokia.com) +** +** This file is part of the documentation of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:LGPL$ +** No Commercial Usage +** This file contains pre-release code and may not be distributed. +** You may use this file in accordance with the terms and conditions +** contained in the Technology Preview License Agreement accompanying +** this package. +** +** GNU Lesser General Public License Usage +** Alternatively, this file may be used under the terms of the GNU Lesser +** General Public License version 2.1 as published by the Free Software +** Foundation and appearing in the file LICENSE.LGPL included in the +** packaging of this file. Please review the following information to +** ensure the GNU Lesser General Public License version 2.1 requirements +** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html. +** +** In addition, as a special exception, Nokia gives you certain +** additional rights. These rights are described in the Nokia Qt LGPL +** Exception version 1.1, included in the file LGPL_EXCEPTION.txt in this +** package. +** +** If you have questions regarding the use of this file, please contact +** Nokia at qt-info@nokia.com. +** +** +** +** +** +** +** +** +** $QT_END_LICENSE$ +** +****************************************************************************/ + +/*! + \page qt4-tulip.html + \title The Tulip Container Classes + + \contentspage {What's New in Qt 4}{Home} + \previouspage What's New in Qt 4 + \nextpage The Interview Framework + + Qt 4 introduces a new set of containers that supersede both the old + QCollection pointer-based containers and the newer QTL value-based + containers. + + \tableofcontents + + \section1 General Overview + + The Tulip containers are similar to Qt 3's QTL containers + (QValueList, QValueVector, QMap), but have the following + advantages: + + \list + \o The containers provide new iterators with a nicer, less + error-prone syntax than STL, inspired by Java's iterators. (The + STL-style iterators are still available as a lightweight, + STL-compatible alternative.) + + \o The containers have been optimized for minimal code expansion. + + \o An empty container performs no memory allocation, and only + requires the same space as a pointer. + + \o Even though they are implicitly shared, they can safely be copied + across different threads without formality. There's no need to use + \c QDeepCopy. + \endlist + + Tulip provides the following sequential containers: QList, + QLinkedList, QVector, QStack, and QQueue. For most + applications, QList is the best type to use. Although it is + implemented as an array-list, it provides very fast prepends and + appends. If you really need a linked-list, use QLinkedList; if you + want your items to occupy consecutive memory locations, use QVector. + QStack and QQueue are convenience classes that provide LIFO and + FIFO semantics. + + Tulip also provides these associative containers: QMap, + QMultiMap, QHash, QMultiHash, and QSet. The "Multi" containers + conveniently support multiple values associated with a single + key. The "Hash" containers provide faster lookup by using a hash + function instead of a binary search on a sorted set. + + The Tulip containers support the \l foreach keyword, a Qt-specific + addition to the C++ language that is implemented using the standard + C++ preprocessor. The syntax is: + + \snippet doc/src/snippets/code/doc_src_qt4-tulip.qdoc 0 + + Example: + + \snippet doc/src/snippets/code/doc_src_qt4-tulip.qdoc 1 + + The iterator variable can also be defined outside the loop. For + example: + + \snippet doc/src/snippets/code/doc_src_qt4-tulip.qdoc 2 + + Just like standard \c for loops, foreach supports braces, \c + break, \c continue, and nested loops. Qt makes a copy of the + container when it enters the loop. If you modify the container as + you are iterating, that won't affect the loop. + + For details about the new containers, see the + \l{Generic Containers} and \l{Generic Algorithms} overview documents. + + In addition to the new containers, considerable work has also gone into + QByteArray and QString. The Qt 3 QCString class has been + merged with QByteArray. The new QByteArray automatically provides + a '\0' terminator after the last character. For example, the byte array + of size 5 containing "abcde" has a null byte at position 5 (one past + the end). This solves all the typical problems that occurred in Qt 3 + with conversions between QByteArray and QCString. + + To avoid crashes, QByteArray::data() never returns a null + pointer. Furthermore, the distinction between null and empty + strings has been watered down so that \c{QByteArray() == + QByteArray("")} and \c{QString() == QString("")}. + + \section1 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: + + \snippet doc/src/snippets/code/doc_src_qt4-tulip.qdoc 3 + + Modifying items using a Java-style iterator: + + \snippet doc/src/snippets/code/doc_src_qt4-tulip.qdoc 4 + + Removing items using a Java-style iterator: + + \snippet doc/src/snippets/code/doc_src_qt4-tulip.qdoc 5 + + Iterating over items with a particular value using STL-style vs. + Java-style iterators: + + \snippet doc/src/snippets/code/doc_src_qt4-tulip.qdoc 6 + + Modifying and removing items using STL-style vs. Java-style + iterators: + + \snippet doc/src/snippets/code/doc_src_qt4-tulip.qdoc 7 + + 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): + + \snippet doc/src/snippets/code/doc_src_qt4-tulip.qdoc 8 + + Retrieving a value from a map, using a default value if the key + doesn't exist: + + \snippet doc/src/snippets/code/doc_src_qt4-tulip.qdoc 9 + + Getting all the values for a particular key in a QMultiMap or QMultiHash: + + \snippet doc/src/snippets/code/doc_src_qt4-tulip.qdoc 10 + + \section1 Comparison with Qt 3 + + Tulip containers are value based. If you want to store a list where + each item is a QWidget *, use QList<QWidget *>. + + The new containers do not support auto-delete. In practice, we + discovered that the only case where auto-delete proved worthwhile was + when the data really should be stored as a value rather than as a + pointer (e.g., QList<int> rather than QList<int *>). If you need + to delete all the items in a container, use qDeleteAll(). + + If you use QValueList in Qt 3, you can replace it with either + QList or QLinkedList in Qt 4. In most cases, QList is the best + choice: It is typically faster, results in less code in your + executable, and requires less memory. However, QLinkedList's + iterators provide stronger guarantees, and only QLinkedList provides + constant-time insertions in the middle, which can make a difference for + lists with thousands of items. + + If you use QValueVector or QMap in Qt 3, the corresponding Qt 4 + classes (QVector, QMap) are very similar to use. +*/ |