diff options
Diffstat (limited to 'src/corelib/doc/snippets/code/src_corelib_tools_qsharedpointer.cpp')
-rw-r--r-- | src/corelib/doc/snippets/code/src_corelib_tools_qsharedpointer.cpp | 157 |
1 files changed, 157 insertions, 0 deletions
diff --git a/src/corelib/doc/snippets/code/src_corelib_tools_qsharedpointer.cpp b/src/corelib/doc/snippets/code/src_corelib_tools_qsharedpointer.cpp new file mode 100644 index 0000000000..e2979fa7b4 --- /dev/null +++ b/src/corelib/doc/snippets/code/src_corelib_tools_qsharedpointer.cpp @@ -0,0 +1,157 @@ +/**************************************************************************** +** +** Copyright (C) 2018 The Qt Company Ltd. +** Contact: https://www.qt.io/licensing/ +** +** This file is part of the documentation of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:BSD$ +** Commercial License Usage +** Licensees holding valid commercial Qt licenses may use this file in +** accordance with the commercial license agreement provided with the +** Software or, alternatively, in accordance with the terms contained in +** a written agreement between you and The Qt Company. For licensing terms +** and conditions see https://www.qt.io/terms-conditions. For further +** information use the contact form at https://www.qt.io/contact-us. +** +** BSD License Usage +** Alternatively, 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 The Qt Company Ltd 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." +** +** $QT_END_LICENSE$ +** +****************************************************************************/ + +//! [0] + class Y: public QEnableSharedFromThis<Y> + { + public: + QSharedPointer<Y> f() + { + return sharedFromThis(); + } + }; + + int main() + { + QSharedPointer<Y> p(new Y()); + QSharedPointer<Y> y = p->f(); + Q_ASSERT(p == y); // p and q must share ownership + } +//! [0] + +//! [1] + class ScriptInterface : public QObject + { + Q_OBJECT + + // ... + + public slots: + void slotCalledByScript(Y *managedBySharedPointer) + { + QSharedPointer<Y> yPtr = managedBySharedPointer->sharedFromThis(); + // Some other code unrelated to scripts that expects a QSharedPointer<Y> ... + } + }; +//! [1] + +//! [2] + static void doDeleteLater(MyObject *obj) + { + obj->deleteLater(); + } + + void otherFunction() + { + QSharedPointer<MyObject> obj = + QSharedPointer<MyObject>(new MyObject, doDeleteLater); + + // continue using obj + obj.clear(); // calls obj->deleteLater(); + } +//! [2] + +//! [3] + QSharedPointer<MyObject> obj = + QSharedPointer<MyObject>(new MyObject, &QObject::deleteLater); +//! [3] + +//! [4] + if (sharedptr) { ... } +//! [4] + +//! [5] + if (!sharedptr) { ... } +//! [5] + +//! [6] + QSharedPointer<T> other(t); this->swap(other); +//! [6] + +//! [7] + QSharedPointer<T> other(t, deleter); this->swap(other); +//! [7] + +//! [8] + if (weakref) { ... } +//! [8] + +//! [9] + if (!weakref) { ... } +//! [9] + +//! [10] + qDebug("Tracking %p", weakref.data()); +//! [10] + +//! [11] + // this pointer cannot be used in another thread + // so other threads cannot delete it + QWeakPointer<int> weakref = obtainReference(); + + Object *obj = weakref.data(); + if (obj) { + // if the pointer wasn't deleted yet, we know it can't get + // deleted by our own code here nor the functions we call + otherFunction(obj); + } +//! [11] + +//! [12] + QWeakPointer<int> weakref; + + // ... + + QSharedPointer<int> strong = weakref.toStrongRef(); + if (strong) + qDebug() << "The value is:" << *strong; + else + qDebug() << "The value has already been deleted"; +//! [12] |