connect returns false

[krivenok]

connect returns false. How can I retrieve detailed description of occured error?

[jacek]

You could catch all qWarning messages using qInstallMsgHandler() or check the arguments yourself using QMetaObject.

[krivenok]

I find many problems in my code, after installing qInstallMsgHandler() handler
But nothing related to connect call

[jacek]

I find many problems in my code, after installing qInstallMsgHandler() handler

All of these warnings are usually written to the console, but on windows you have to add CONFIG += console to your .pro file (or use your own message handler) to see them.

But nothing related to connect call

Try compiling your program in debug mode (CONFIG += debug in the .pro file).

[drow]

what's your proble?
do you can post yuor code?

[krivenok]

The code below is QT's connect implementation.

bool QObject::connect(const QObject *sender, const char *signal,
const QObject *receiver, const char *method,
Qt::ConnectionType type)
{
#ifndef QT_NO_DEBUG
bool warnCompat = true;
#endif
if (type == Qt::AutoCompatConnection) {
type = Qt::AutoConnection;
#ifndef QT_NO_DEBUG
warnCompat = false;
#endif
}

if (sender == 0 || receiver == 0 || signal == 0 || method == 0) {
#ifndef QT_NO_DEBUG
qWarning("Object::connect: Cannot connect %s::%s to %s::%s",
sender ? sender->metaObject()->className() : "(null)",
signal ? signal+1 : "(null)",
receiver ? receiver->metaObject()->className() : "(null)",
method ? method+1 : "(null)");
#endif
return false;
}
QByteArray tmp_signal_name;

#ifndef QT_NO_DEBUG
if (!check_signal_macro(sender, signal, "connect", "bind"))
return false;
#endif
const QMetaObject *smeta = sender->metaObject();
++signal; //skip code
int signal_index = smeta->indexOfSignal(signal);
if (signal_index < 0) {
// check for normalized signatures
tmp_signal_name = QMetaObject::normalizedSignature(signal).prepend(* (signal - 1));
signal = tmp_signal_name.constData() + 1;
signal_index = smeta->indexOfSignal(signal);
if (signal_index < 0) {
#ifndef QT_NO_DEBUG
err_method_notfound(QSIGNAL_CODE, sender, signal, "connect");
err_info_about_objects("connect", sender, receiver);
#endif
return false;
}
}

QByteArray tmp_method_name;
int membcode = method[0] - '0';

#ifndef QT_NO_DEBUG
if (!check_method_code(membcode, receiver, method, "connect"))
return false;
#endif
++method; // skip code

const QMetaObject *rmeta = receiver->metaObject();
int method_index = -1;
switch (membcode) {
case QSLOT_CODE:
method_index = rmeta->indexOfSlot(method);
break;
case QSIGNAL_CODE:
method_index = rmeta->indexOfSignal(method);
break;
}
if (method_index < 0) {
// check for normalized methods
tmp_method_name = QMetaObject::normalizedSignature(method);
method = tmp_method_name.constData();
switch (membcode) {
case QSLOT_CODE:
method_index = rmeta->indexOfSlot(method);
break;
case QSIGNAL_CODE:
method_index = rmeta->indexOfSignal(method);
break;
}
}

if (method_index < 0) {
#ifndef QT_NO_DEBUG
err_method_notfound(membcode, receiver, method, "connect");
err_info_about_objects("connect", sender, receiver);
#endif
return false;
}
#ifndef QT_NO_DEBUG
if (!QMetaObject::checkConnectArgs(signal, method)) {
qWarning("Object::connect: Incompatible sender/receiver arguments"
"\n\t%s::%s --> %s::%s",
sender->metaObject()->className(), signal,
receiver->metaObject()->className(), method);
return false;
}
#endif

int *types = 0;
if (type == Qt::QueuedConnection
&& !(types = ::queuedConnectionTypes(smeta->method(signal_index).parameterTypes())))
return false;

#ifndef QT_NO_DEBUG
{
QMetaMethod smethod = smeta->method(signal_index);
QMetaMethod rmethod = rmeta->method(method_index);
if (warnCompat) {
if(smethod.attributes() & QMetaMethod::Compatibility) {
if (!(rmethod.attributes() & QMetaMethod::Compatibility))
qWarning("Object::connect: Connecting from COMPAT signal (%s::%s).", smeta->className(), signal);
} else if(rmethod.attributes() & QMetaMethod::Compatibility && membcode != QSIGNAL_CODE) {
qWarning("Object::connect: Connecting from %s::%s to COMPAT slot (%s::%s).",
smeta->className(), signal, rmeta->className(), method);
}
}
}
#endif
QMetaObject::connect(sender, signal_index, receiver, method_index, type, types);
const_cast<QObject*>(sender)->connectNotify(signal - 1);
return true;
}

[wysota]

I think preposter meant your code and not Qt code