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qscopedvaluerollback: add convenience constructor

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It's a common need to assign a variable to something when entering a
code block, and then revert it upon exit. qscopedvaluerollback can
be used for this. But as a convenience, this patch adds an
extra constructor so that you can "protect" and set a variable
in one go instead of using two lines.

Change-Id: If4b89d3a5ba32ef2304bda058b1b6050932612ed
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
This commit is contained in:
Richard Moe Gustavsen 2014-05-14 10:52:37 +02:00 committed by The Qt Project
parent aefa611f0c
commit 77982c4823
3 changed files with 23 additions and 3 deletions
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11
src/corelib/tools/qscopedvaluerollback.cpp
View File

@ -1,6 +1,6 @@
/****************************************************************************
**
** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
**
** This file is part of the QtCore module of the Qt Toolkit.
@ -69,6 +69,15 @@ QT_BEGIN_NAMESPACE
Stores the previous value of \a var internally, for revert on destruction.
*/
/*!
\fn QScopedValueRollback::QScopedValueRollback(T &var, T value)
Assigns \a value to \ var and stores the previous value of \a var
internally, for revert on destruction.
\since 5.4
*/
/*!
\fn QScopedValueRollback::~QScopedValueRollback()

9
src/corelib/tools/qscopedvaluerollback.h
View File

@ -1,6 +1,6 @@
/****************************************************************************
**
** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
**
** This file is part of the QtCore module of the Qt Toolkit.
@ -56,6 +56,13 @@ public:
oldValue = varRef;
}
explicit QScopedValueRollback(T &var, T value) :
varRef(var)
{
oldValue = varRef;
varRef = value;
}
~QScopedValueRollback()
{
varRef = oldValue;

6
tests/auto/corelib/tools/qscopedvaluerollback/tst_qscopedvaluerollback.cpp
View File

@ -1,6 +1,6 @@
/****************************************************************************
**
** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
**
** This file is part of the test suite of the Qt Toolkit.
@ -67,14 +67,17 @@ void tst_QScopedValueRollback::leavingScope()
{
int i = 0;
bool b = false;
bool b2 = false;
QString s("This is useful");
//test rollback on going out of scope
{
QScopedValueRollback<int> ri(i);
QScopedValueRollback<bool> rb(b);
QScopedValueRollback<bool> rb2(b2, true);
QScopedValueRollback<QString> rs(s);
QCOMPARE(b, false);
QCOMPARE(b2, true);
QCOMPARE(i, 0);
QCOMPARE(s, QString("This is useful"));
b = true;
@ -85,6 +88,7 @@ void tst_QScopedValueRollback::leavingScope()
QCOMPARE(s, QString("Useless"));
}
QCOMPARE(b, false);
QCOMPARE(b2, false);
QCOMPARE(i, 0);
QCOMPARE(s, QString("This is useful"));
}