CODEWITHSUNDEEP
c++qt
vico
vico

Reputation: 18251

QT logging with text formatting

According manual in order to log into file I need to open it in main:

QScopedPointer<QFile>   m_logFile;

void messageHandler(QtMsgType type, const QMessageLogContext &context, const QString &msg);
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    m_logFile.reset(new QFile("logFile.txt"));

    m_logFile.data()->open(QFile::Append | QFile::Text);
    qInstallMessageHandler(messageHandler);

    MainWindow w;
    w.show();

    return a.exec();
}

Then I can log to it:

qDebug(logDebug()) << "Hello Debug";

But how to organize logging in more convenient way with text formatting like printf:

printf("Hello Debug %d, my_int);

Upvotes: 1

Views: 1845

Answers (3)

Mihayl
Mihayl

Reputation: 3911

Additionally to stream-like API you can simply use qDebug like printf. 

qDebug("Hello Debug %d", my_int);

Similar with logging category:

qCDebug(category, "Hello Debug %d", my_int);

Tip

The following message format produces nice links to the lines printed the trace in the QtCreator's Application Output pane.

QT_MESSAGE_PATTERN=[%{time process}] %{threadid} file:/%{file}:%{line}: %{message} %{if-critical}%{backtrace}%{endif}

Upvotes: 3

Paul
Paul

Reputation: 13238

You can use QString::asprintf() or, preferably QString::arg() to produce QString using printf-like format syntax and then use it with qDebug().

Upvotes: 0

Pavan Chandaka
Pavan Chandaka

Reputation: 12831

you can simply write the integer object.

qDebug(logDebug()) << "Hello Debug "<< my_int;

or

qDebug(logDebug()) << "Hello Debug"<< " "<<my_int;

Upvotes: 0

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