QMessageLogger Class

The QMessageLogger class generates log messages. More...

Header: #include <QMessageLogger>
qmake: QT += core
Since: Qt 5.0

Public Functions

QMessageLogger()
QMessageLogger(const char * file, int line, const char * function)
QMessageLogger(const char * file, int line, const char * function, const char * category)
void critical(const char * msg, ...) const
QDebug critical() const
void debug(const char * msg, ...) const
QDebug debug() const
void fatal(const char * msg, ...) const
void warning(const char * msg, ...) const
QDebug warning() const

Detailed Description

The QMessageLogger class generates log messages.

QMessageLogger is used to generate messages for the Qt logging framework. Usually one uses it through qDebug(), qWarning(), qCritical, or qFatal() functions, which are actually macros that expand to QMessageLogger(__FILE__, __LINE__, Q_FUNC_INFO).debug() et al.

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 QMessageLogContext, qDebug(), qWarning(), qCritical(), and qFatal().

Member Function Documentation

QMessageLogger::QMessageLogger()

Constructs a default QMessageLogger. See the other constructors to specify context information.

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")

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 qCritical().

QDebug QMessageLogger::critical() const

Logs a critical message using a QDebug stream

See also qCritical() and 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 qDebug().

QDebug QMessageLogger::debug() const

Logs a debug message using a QDebug stream

See also qDebug() and QDebug.

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 qFatal().

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 qWarning().

QDebug QMessageLogger::warning() const

Logs a debug message using a QDebug stream

See also qWarning() and QDebug.