[Solved] Printable Object

Thanatos.jsse

Hi everyone,

I need made a custom printable QObject printable, I follow the qt "doc":http://qt-project.org/doc/qt-4.8/custom-types.html#making-the-type-printabledoc but can't use this successfully.

@MyObject : public QObject
{
Q_OBJECT
MyObject() : m_str("Hello world") {}
MyObject(const MyObject &o) : m_str(o.m_str) {}
~MyObject() {}

private:
QString m_str;

}
Q_DECLARE_METATYPE(MyObject)

QDebug operator <<(QDebug &, const MyObject &); /* trivial definition in *.cpp file */
@

If I try to use qDebug() << MyClass I've got: no match for 'operator<<' in 'QDebug()() << MyClass'
@/* main.cpp */
MyClass m;
qDebug() << m;@

I need print my custom object for debug purposes.

Thank you in advice.

BR,

mairesse

Edit: I'm really sorry, I tried to answer your question but it happened that I did it extremely wrong, I'll search for a possible solution and if I find anything out I come back here and edit my post to help you.

Sorry again hehe.

giesbert

Hi,

first of all, MyClass != MyObject.
Are you sure, the code is the one you use?
I ask because I get compile errors others then the one you had.
This code works for me:

@
#include <QObject>
#include <QDebug>

class MyObject : public QObject
{
Q_OBJECT
public:
MyObject() : m_str("Hello world") {}
MyObject(const MyObject &o) : m_str(o.m_str) {}
~MyObject() {}

private:
QString m_str;
friend QDebug& operator << (QDebug& debug, const MyObject& myObj);
};

Q_DECLARE_METATYPE(MyObject)

inline QDebug& operator << (QDebug& debug, const MyObject& myObj)
{
debug.nospace() << '(';
debug << "MyObject(" << myObj.m_str << ")";
return debug.space();
}

int main(int argc, char *argv[])
{
MyObject m;
qDebug() << m;

return 0;

}

@

Thanatos.jsse

Hi Gerolf,

Thank for your reply.

Yes, MyClass != MyObject (I'm sorry, it was a typographic mistake).
I have found the error (but I can't understand), your definition don't work for me:

When we see this definition anything is wrong, it's a simple operator overload, but don't work when use & in QDebug parameter (dbg reference), I have to eliminate this from you code and it work.

@Debug &operator <<(QDebug dbg, const MyObject &myObj)@

But I can't understand why can't pass QDebug like reference.

Thank you Gerolf.

BR,