[Qt-interest] Design Patterns

[Alan Ezust]

Ross Bencina wrote:


> Qt implements quite a few design patterns:
>
> Abstract Factory:
> QMetaObject::newInstance()
> http://doc.trolltech.com/4.5/qmetaobject.html
>
> Adapter / Proxy:
> QGraphicsProxyWidget (adapts QWidget into a QGraphicsItem)
> http://doc.trolltech.com/4.5/qgraphicsproxywidget.html
>
> Composite:
> QObject / QWidget
> http://doc.trolltech.com/4.5/qobject.html
> http://doc.trolltech.com/4.5/qwidget.html
>
> Facade:
> QListWidget, QTreeWidget, QTableWidget
> http://doc.trolltech.com/4.5/qlistwidget.html
> http://doc.trolltech.com/4.5/qtreewidget.html
> http://doc.trolltech.com/4.5/qtablewidget.html
>
> Chain of Responsibility:
> QWidget and QGraphicsItem event bubbling
>
> Command:
> QUndoCommand
> http://doc.trolltech.com/4.5/qundocommand.html
>
> Interpreter:
> QScriptEngine:
> http://doc.trolltech.com/4.5/qscriptengine.html
>
> Memento:
> QByteArray in QMainWindow::saveState() / restoreState()
>
> Observer:
> Signals & Slots
> Model/View framework
> http://doc.trolltech.com/4.5/model-view-programming.html
>
> Any others in Qt?
>
>
I think the whole point of design patterns is that it is the foundation on
which many of the classes in Qt were built, and if you know what they are
and how to reuse them, that will save you lots of work later.

Your list was great, I have a similar one and I added a couple of yours to
it. But here are some additions :-)

Composite:
QObject, QWidget, QGraphicsItem, QTreeWidgetItem, QDomNode,
QHelpContentItem, QResource

Decorator:
QScrollArea, QTabWidget, and I'm sure many more

Facade:
QFile, QProcess, QThread, QTreeWidget, QSqlDatabase, QString, and many
others

Reflection Pattern:
QMetaObject, QMetaProperty

Iterator Pattern:
iterator, Iterator, and foreach loops

Visitor Pattern
QTeeWidgetItemIterator, QWizard (a visitor for QWizardPages)

Singleton:
QApplication, QPluginLoader::staticInstances()]

Monostate:
QSettings

Factory Method:
QFileIconProvider QDomDocument::createElement()

Abstract Factory:
QMetaObject::newInstance(),  QImageIOPlugin, QItemEditorFactory,
QAbstractExtensionFactory

Mediator:
QAbstractItemDelegate


> If you're looking for another enlightening read try Martin Fowler's
> "Refactoring" -- another Addison Wesley book which changed my life.
>
> I agree with that, Refactoring is excellent.

Another good book (shameless plug) is called Introduction to Design Patterns
in C++ and Qt4.

http://www.amazon.com/gp/product/0131879057/sr=8-2/qid=1149695799/ref=pd_bbs_2/103-4972622-0091013?_encoding=UTF8
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