summaryrefslogtreecommitdiffstats
path: root/doc/src/declarative/propertybinding.qdoc
diff options
context:
space:
mode:
authoraxis <qt-info@nokia.com>2010-02-16 11:53:07 (GMT)
committeraxis <qt-info@nokia.com>2010-02-16 11:53:07 (GMT)
commit15b08dffc1354bc816b04901a7442679382b0935 (patch)
tree783af85b75f9de3ab10902c5ba66cf5e22b2fe61 /doc/src/declarative/propertybinding.qdoc
parent9f5b02406f38fe02a27de7843b9f8a11232d2064 (diff)
parent9d174f13e48730ac06aa429e0f011a02b333025e (diff)
downloadQt-15b08dffc1354bc816b04901a7442679382b0935.zip
Qt-15b08dffc1354bc816b04901a7442679382b0935.tar.gz
Qt-15b08dffc1354bc816b04901a7442679382b0935.tar.bz2
Merge branch 'master' of scm.dev.nokia.troll.no:qt/qt-s60-public
Conflicts: configure mkspecs/common/symbian/symbian.conf mkspecs/features/symbian/application_icon.prf qmake/generators/makefile.cpp qmake/generators/symbian/initprojectdeploy_symbian.cpp qmake/generators/symbian/symmake.cpp tools/assistant/tools/assistant/assistant.pro
Diffstat (limited to 'doc/src/declarative/propertybinding.qdoc')
-rw-r--r--doc/src/declarative/propertybinding.qdoc110
1 files changed, 110 insertions, 0 deletions
diff --git a/doc/src/declarative/propertybinding.qdoc b/doc/src/declarative/propertybinding.qdoc
new file mode 100644
index 0000000..ad4f13e
--- /dev/null
+++ b/doc/src/declarative/propertybinding.qdoc
@@ -0,0 +1,110 @@
+/****************************************************************************
+**
+** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** Contact: Qt Software Information (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 either Technology Preview License Agreement or the
+** Beta Release License Agreement.
+**
+** 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 1.0, included in the file LGPL_EXCEPTION.txt in this
+** package.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+**
+** If you are unsure which license is appropriate for your use, please
+** contact the sales department at qt-sales@nokia.com.
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+/*!
+\page propertybinding.html
+\title Property Binding
+
+Property binding is a declarative way of specifying the value of a property. Binding allows
+a property's value to be expressed as an JavaScript expression that defines the value relative
+to other property values or data accessible in the application. The property value is
+automatically kept up to date if the other properties or data values change.
+
+Property bindings are created implicitly in QML whenever a property is assigned an JavaScript
+expression. The following QML uses two property bindings to connect the size of the rectangle
+to that of \c otherItem.
+
+\code
+Rectangle {
+ width: otherItem.width
+ height: otherItem.height
+}
+\endcode
+
+QML extends a standards compliant JavaScript engine, so any valid JavaScript expression can be
+used as a property binding. Bindings can access object properties, make function calls and even
+use builtin JavaScript objects like \e {Date} and \e {Math}. Assigning a constant value to a
+property can even be thought of as a binding - afterall, a constant is a valid JavaScript
+expression! Here are some examples of more complex bindings:
+
+\code
+Rectangle {
+ Script {
+ function calculateMyHeight() {
+ return Math.max(otherItem.height, thirdItem.height);
+ }
+ }
+
+ anchors.centerIn: parent
+ width: Math.min(otherItem.width, 10)
+ height: calculateMyHeight()
+ color: { if (width > 10) "blue"; else "red" }
+}
+\endcode
+
+Being JavaScript expressions, bindings are evaluated in a scope chain. The \l {QML Scope}
+documentation covers the specifics of scoping in QML.
+
+\list
+\o When does a binding not get updated?
+\o Scope
+\o Assigning a constant/other binding clears existing binding
+\o Loops
+\o Using model data
+\endlist
+
+\section1 Binding Element
+
+The implicit binding syntax shown previously is easy to use and works perfectly for most uses
+of bindings. In some advanced cases, it is necessary to create bindings explicitly using the
+\l Binding element.
+
+For example, to bind a property exposed from C++ (\c system.brightness) to a value
+coming from QML (\c slider.value), you could use the Binding element as follows:
+\qml
+Binding {
+ target: system
+ property: "brightness"
+ value: slider.value
+}
+\endqml
+*/
+