QMessageLogger Class▲
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Header: QMessageLogger
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Since: Qt 5.0
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CMake:
find_package(Qt6 REQUIRED COMPONENTS Core)
target_link_libraries(mytarget PRIVATE Qt6::Core)
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qmake: QT += core
Detailed Description▲
QMessageLogger is used to generate messages for the Qt logging framework. Usually one uses it through qDebug(), qInfo(), qWarning(), qCritical, or qFatal() functions, which are actually macros: For example qDebug() expands to QMessageLogger(__FILE__, __LINE__, Q_FUNC_INFO).debug() for debug builds, and QMessageLogger(0, 0, 0).debug() for release builds.
One example of direct use is to forward errors that stem from a scripting language, e.g. QML:
void statusChanged(QDeclarativeComponent::Status status) {
if (status == QDeclarativeComponent::Error) {
foreach (const QDeclarativeError &error, component->errors()) {
const QByteArray file = error.url().toEncoded();
QMessageLogger(file.constData(), error.line(), 0).debug() << error.description();
}
}
}See Also▲
Member Type Documentation▲
[since 5.3] QMessageLogger::CategoryFunction▲
This is a typedef for a pointer to a function with the following signature:
const QLoggingCategory &category();The Q_DECLARE_LOGGING_CATEGORY macro generates a function declaration with this signature, and Q_LOGGING_CATEGORY generates its definition.
This typedef was introduced in Qt 5.3.
Member Function Documentation▲
[constexpr] QMessageLogger::QMessageLogger()▲
Constructs a default QMessageLogger. See the other constructors to specify context information.
[constexpr] QMessageLogger::QMessageLogger(const char *file, int line, const char *function)▲
Constructs a QMessageLogger to record log messages for file at line in function. The is equivalent to QMessageLogger(file, line, function, "default")
[constexpr] QMessageLogger::QMessageLogger(const char *file, int line, const char *function, const char *category)▲
Constructs a QMessageLogger to record category messages for file at line in function.
void QMessageLogger::critical(const char *msg, ...) const▲
Logs a critical message specified with format msg. Additional parameters, specified by msg, may be used.
See Also▲
See also qCritical()
[since 5.3] void QMessageLogger::critical(const QLoggingCategory &cat, const char *msg, ...) const▲
Logs a critical message specified with format msg for the context cat. Additional parameters, specified by msg, may be used.
This function was introduced in Qt 5.3.
See Also▲
See also qCCritical()
[since 5.3] void QMessageLogger::critical(QMessageLogger::CategoryFunction catFunc, const char *msg, ...) const▲
Logs a critical message specified with format msg for the context returned by catFunc. Additional parameters, specified by msg, may be used.
This function was introduced in Qt 5.3.
See Also▲
See also qCCritical()
QDebug QMessageLogger::critical() const▲
[since 5.3] QDebug QMessageLogger::critical(const QLoggingCategory &cat) const▲
Logs a critical message into category cat using a QDebug stream.
This function was introduced in Qt 5.3.
See Also▲
See also qCCritical(), QDebug
[since 5.3] QDebug QMessageLogger::critical(QMessageLogger::CategoryFunction catFunc) const▲
Logs a critical message into category returned by catFunc using a QDebug stream.
This function was introduced in Qt 5.3.
See Also▲
See also qCCritical(), QDebug
void QMessageLogger::debug(const char *msg, ...) const▲
Logs a debug message specified with format msg. Additional parameters, specified by msg, may be used.
See Also▲
See also qDebug()
[since 5.3] void QMessageLogger::debug(const QLoggingCategory &cat, const char *msg, ...) const▲
Logs a debug message specified with format msg for the context cat. Additional parameters, specified by msg, may be used.
This function was introduced in Qt 5.3.
See Also▲
See also qCDebug()
[since 5.3] void QMessageLogger::debug(QMessageLogger::CategoryFunction catFunc, const char *msg, ...) const▲
Logs a debug message specified with format msg for the context returned by catFunc. Additional parameters, specified by msg, may be used.
This function was introduced in Qt 5.3.
See Also▲
See also qCDebug()
QDebug QMessageLogger::debug() const▲
[since 5.3] QDebug QMessageLogger::debug(const QLoggingCategory &cat) const▲
Logs a debug message into category cat using a QDebug stream.
This function was introduced in Qt 5.3.
See Also▲
[since 5.3] QDebug QMessageLogger::debug(QMessageLogger::CategoryFunction catFunc) const▲
Logs a debug message into category returned by catFunc using a QDebug stream.
This function was introduced in Qt 5.3.
See Also▲
void QMessageLogger::fatal(const char *msg, ...) const▲
Logs a fatal message specified with format msg. Additional parameters, specified by msg, may be used.
See Also▲
See also qFatal()
[since 5.5] void QMessageLogger::info(const char *msg, ...) const▲
Logs an informational message specified with format msg. Additional parameters, specified by msg, may be used.
This function was introduced in Qt 5.5.
See Also▲
See also qInfo()
[since 5.5] void QMessageLogger::info(const QLoggingCategory &cat, const char *msg, ...) const▲
Logs an informational message specified with format msg for the context cat. Additional parameters, specified by msg, may be used.
This function was introduced in Qt 5.5.
See Also▲
See also qCInfo()
[since 5.5] void QMessageLogger::info(QMessageLogger::CategoryFunction catFunc, const char *msg, ...) const▲
Logs an informational message specified with format msg for the context returned by catFunc. Additional parameters, specified by msg, may be used.
This function was introduced in Qt 5.5.
See Also▲
See also qCInfo()
[since 5.5] QDebug QMessageLogger::info() const▲
Logs an informational message using a QDebug stream.
This function was introduced in Qt 5.5.
See Also▲
[since 5.5] QDebug QMessageLogger::info(const QLoggingCategory &cat) const▲
Logs an informational message into the category cat using a QDebug stream.
This function was introduced in Qt 5.5.
See Also▲
[since 5.5] QDebug QMessageLogger::info(QMessageLogger::CategoryFunction catFunc) const▲
Logs an informational message into category returned by catFunc using a QDebug stream.
This function was introduced in Qt 5.5.
See Also▲
void QMessageLogger::warning(const char *msg, ...) const▲
Logs a warning message specified with format msg. Additional parameters, specified by msg, may be used.
See Also▲
See also qWarning()
[since 5.3] void QMessageLogger::warning(const QLoggingCategory &cat, const char *msg, ...) const▲
Logs a warning message specified with format msg for the context cat. Additional parameters, specified by msg, may be used.
This function was introduced in Qt 5.3.
See Also▲
See also qCWarning()
[since 5.3] void QMessageLogger::warning(QMessageLogger::CategoryFunction catFunc, const char *msg, ...) const▲
Logs a warning message specified with format msg for the context returned by catFunc. Additional parameters, specified by msg, may be used.
This function was introduced in Qt 5.3.
See Also▲
See also qCWarning()