<![CDATA[isSignalConnected correct usage]]>to check if a signal is connected I use this code:

    if (!this->isSignalConnected(QMetaMethod::fromSignal(&QtVariantPropertyManager::propertyChanged))) {

        connect( sdkItemPropManager, SIGNAL( propertyChanged( QtProperty * ) ), this, SLOT( onUpdatePropertyValues() ) );
        connect( sdkEmuManager, SIGNAL( propertyChanged( QtProperty * ) ), this, SLOT( onUpdatePropertyValues() ) );

    }

But I always got an Assert:

ASSERT failure in QObject::isSignalConnected: "the parameter must be a signal member of the object", file \Users\qt\work\qt\qtbase\src\corelib\kernel\qobject.cpp, line 2539

Is there an explanation that you can understand?

]]>https://forum.qt.io/topic/126435/issignalconnected-correct-usageRSS for NodeTue, 21 Apr 2026 17:43:09 GMTFri, 07 May 2021 12:31:36 GMT60<![CDATA[Reply to isSignalConnected correct usage on Fri, 07 May 2021 15:21:50 GMT]]>@pixbyte
Hence I presume the message

"signal must be a signal member of this object, otherwise the behaviour is undefined."

in answer to your

But also Iam interrested why the initial code do not work.

]]>https://forum.qt.io/post/658539https://forum.qt.io/post/658539Fri, 07 May 2021 15:21:50 GMT<![CDATA[Reply to isSignalConnected correct usage on Fri, 07 May 2021 14:54:26 GMT]]>No this is the target where the signal is connected on. I think here it is a mdi_child.

]]>https://forum.qt.io/post/658534https://forum.qt.io/post/658534Fri, 07 May 2021 14:54:26 GMT<![CDATA[Reply to isSignalConnected correct usage on Fri, 07 May 2021 14:37:09 GMT]]>@pixbyte
I assume as the error message states.

this->isSignalConnected(QMetaMethod::fromSignal(&QtVariantPropertyManager::propertyChanged)

Is this of type QtVariantPropertyManager?

]]>https://forum.qt.io/post/658526https://forum.qt.io/post/658526Fri, 07 May 2021 14:37:09 GMT<![CDATA[Reply to isSignalConnected correct usage on Fri, 07 May 2021 14:27:42 GMT]]>@Christian-Ehrlicher said in isSignalConnected correct usage:

Qt::UniqueConnection

ok, this is really a good and helpfull tip. Thank you. But also Iam interrested why the initial code do not work.

]]>https://forum.qt.io/post/658521https://forum.qt.io/post/658521Fri, 07 May 2021 14:27:42 GMT<![CDATA[Reply to isSignalConnected correct usage on Fri, 07 May 2021 12:36:34 GMT]]>Why not simply use Qt::UniqueConnection?

According to the documentation: "signal must be a signal member of this object, otherwise the behaviour is undefined."

]]>https://forum.qt.io/post/658496https://forum.qt.io/post/658496Fri, 07 May 2021 12:36:34 GMT