How to enable and disable qDebug() messages inside a class

LeLev

Hi,
In my Qt5 project i have multiple classes, inside each class they are a few

qDebug() << message;

is it possible to enable/disable this qDebug() lines in a particular classe ?

exemple of what i want to do :

class A: public QObject
{
    Q_OBJECT
public:
       A();
    ~A(){}

    Q_INVOKABLE void connecToServer(){
        conn->start();
        if(dbg){
            qDebug()<<"started !"
        }
    }
private:
  bool dbg = true;  
};

Is there a way to do this without de 'if' statement ?

Thx in advance
LA

jsulm

@LeLev See https://doc.qt.io/qt-5.10/debug.html
"qDebug(), qInfo(), and qWarning() are debugging tools. They can be compiled away by defining QT_NO_DEBUG_OUTPUT, QT_NO_INFO_OUTPUT, or QT_NO_WARNING_OUTPUT during compilation."

LeLev

@jsulm Thx, but as i said I want do disable qDebug() for a particular class.
with QT_NO_DEBUG_OUTPUT i will disable for the whole application no ?

jsulm

@LeLev I don't understand the use case. How do you decide whether to activate debug output for a specific class and when do you decide (compile time? run time?)?

LeLev

@jsulm sorry..
My probleme is : i have lot of messages, so i can't focus on the message i'm interested.

For the moment i'm testing my application, i just want to enable/disable output messages in a particular class, just before running the app.
So lets say i have a classes A, B and C. I want to disable messages comming from B and C, and only see messages from A.
Am I more understandable ?
Thx

jsulm

@LeLev

#define DEBUG
class A: public QObject
{
    Q_OBJECT
public:
       A();
    ~A(){}

    Q_INVOKABLE void connecToServer(){
        conn->start();
#ifdef DEBUG
            qDebug()<<"started !"
#endif
        }
    }
private:
  bool dbg = true;  
};

LeLev

@jsulm Perfect ! Thx :)

aha_1980

Hi @LeLev,

you might also be interested in Qt's categorized logging function: http://blog.qt.io/blog/2014/03/11/qt-weekly-1-categorized-logging/

With that, you can enable/disable logging at runtime. You just need to replace qDebug by qCDebug and add appropriate categories.

Regards.

LeLev

Thx @aha_1980 ! i will check that too.

JonB

@LeLev
You should probably also be aware of https://doc.qt.io/qt-5.10/qtglobal.html#qInstallMessageHandler

qInstallMessageHandler allows you to control what happens at run-time (instead of compile time) to anything going via qDebug(), qWarn() etc., whether from your own code or Qt internals.