From b6e78b38367a23f0b053bbd2abe4ef161e4053b9 Mon Sep 17 00:00:00 2001 From: Chris Adams Date: Mon, 6 Feb 2012 14:24:42 +1000 Subject: Improve support for var properties This commit changes the semantics of function assignment in QML. Previously, function assignment was interpreted as binding assignment. Now, function assignment is interpreted as function assignment, and therefore fails for all property types other than "var" properties. To support imperative binding assignment, a new function was added to the Qt object: Qt.binding(function) which takes a single function parameter and returns a function object which will be interpreted as an assignable binding expression by the QML engine. Finally, this commit also slightly changes the semantics of var properties in that the "special" JavaScript values of null and undefined may be assigned to var properties, rather than being interpreted as reset requests. Task-number: QTBUG-21842 Change-Id: Iee99a878b9badf0fb76e983da7ebfa493f55ceb5 Reviewed-by: Matthew Vogt --- doc/src/snippets/qml/qtBinding.1.qml | 55 ++++++++++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+) create mode 100644 doc/src/snippets/qml/qtBinding.1.qml (limited to 'doc/src/snippets/qml/qtBinding.1.qml') diff --git a/doc/src/snippets/qml/qtBinding.1.qml b/doc/src/snippets/qml/qtBinding.1.qml new file mode 100644 index 0000000000..acec88a47f --- /dev/null +++ b/doc/src/snippets/qml/qtBinding.1.qml @@ -0,0 +1,55 @@ +/**************************************************************************** +** +** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies). +** Contact: http://www.qt-project.org/ +** +** This file is part of the documentation of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:BSD$ +** You may use this file under the terms of the BSD license as follows: +** +** "Redistribution and use in source and binary forms, with or without +** modification, are permitted provided that the following conditions are +** met: +** * Redistributions of source code must retain the above copyright +** notice, this list of conditions and the following disclaimer. +** * Redistributions in binary form must reproduce the above copyright +** notice, this list of conditions and the following disclaimer in +** the documentation and/or other materials provided with the +** distribution. +** * Neither the name of Nokia Corporation and its Subsidiary(-ies) nor +** the names of its contributors may be used to endorse or promote +** products derived from this software without specific prior written +** permission. +** +** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS +** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR +** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT +** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT +** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, +** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY +** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT +** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE +** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE." +** +** $QT_END_LICENSE$ +** +****************************************************************************/ + +import QtQuick 2.0 + +//![0] +Item { + property bool someCondition: true + property int edgePosition + + Component.onCompleted: { + if (someCondition == true) { + // bind to the result of the binding expression passed to Qt.binding() + edgePosition = Qt.binding(function() { return x + width }) + } + } +} +//![0] -- cgit v1.2.3