QDebugStateSaver Class

Convenience class for custom QDebug operators.

This class was introduced in Qt 5.1.

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Publié le 26 janvier 2024 - Mis à jour le 26 janvier 2024

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QDebugStateSaver Class▲

Header: QDebugStateSaver
Since: Qt 5.1
CMake:

find_package(Qt6 REQUIRED COMPONENTS Core)

target_link_libraries(mytarget PRIVATE Qt6::Core)
qmake: QT += core

Detailed Description▲

Saves the settings used by QDebug, and restores them upon destruction, then calls maybeSpace(), to separate arguments with a space if autoInsertSpaces() was true at the time of constructing the QDebugStateSaver.

The automatic insertion of spaces between writes is one of the settings that QDebugStateSaver stores for the duration of the current block.

The settings of the internal QTextStream are also saved and restored, so that using << Qt::hex in a QDebug operator doesn't affect other QDebug operators.

QDebugStateSaver is typically used in the implementation of an operator<<() for debugging:

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QDebug operator&lt;&lt;(QDebug dbg, const Message &amp;message)
{
    QDebugStateSaver saver(dbg);
    QList&lt;QStringView&gt; pieces = message.body().split(u"\r\n", Qt::SkipEmptyParts);
    if (pieces.isEmpty())
        dbg.nospace() &lt;&lt; "Message()";
    else if (pieces.size() == 1)
        dbg.nospace() &lt;&lt; "Message(" &lt;&lt; pieces.first() &lt;&lt; ")";
    else
        dbg.nospace() &lt;&lt; "Message(" &lt;&lt; pieces.first() &lt;&lt; " ...)";
    return dbg;
}

Member Function Documentation▲

QDebugStateSaver::QDebugStateSaver(QDebug &dbg)▲

Creates a QDebugStateSaver instance, which saves the settings currently used by dbg.

QDebugStateSaver::~QDebugStateSaver()▲

Destroys a QDebugStateSaver instance, which restores the settings used when the QDebugStateSaver instance was created.