QObject::connect: Cannot queue arguments of type 'xxx&'(Make sure 'xxx&' is registered using qRegisterMetaType().)

[opengpu2]

QObject::connect: Cannot queue arguments of type 'xxx&'
(Make sure 'xxx&' is registered using qRegisterMetaType().)

[mcosta]

Hi,

what is the question?
Can you show your code?

[opengpu2]

@mcosta QObject::connnect(), the signal and slot i use signal(const xxx&)
xxx is the param type

and i saw the warning above in the VS output...

[mcosta]

what xxx is??

if you are using a custom type you have to register it to be used in MetaType system

[opengpu2]

@mcosta xxx is my own Class

[opengpu2]

@opengpu2 how to register it? i did not register...and it seems to work fine...

[mcosta]

To register a custom type you have to use qRegisterMetaType(). You need to use it if you use QueuedConnection.

Read here for more details

[opengpu2]

@mcosta yeh, the sender and reciever are in 2 threads, so its AutoConnection is QueuedConnection

is my own custom Class must have defalut constructor?
what should i do if my Class only have constructor with param?

[nand]

I too faced with same situation..
code:@{
connect(serial,SIGNAL(func(cv::String,cv::Mat,QTextStream&)),this,SLOT(func(cv::String,cv::Mat,QTextStream&)));
}@
Error:
Cannot queue arguments of type 'QTextstream&'

I got same error for cv::string & cv::Mat but i resolved it using:
qRegisterMetaType< cv::Mat >("cv::Mat");
qRegisterMetaType< cv::String >("cv::String");
but am unable to fix it for QTextstream&
Would you please help me here?

[mrjj]

@nand said:

Cannot queue arguments of type 'QTextstream&'

Have you tried with QTextstream*'
just to see if it like that `?

Edit:
It solved the issue.

[jsulm]

Actually there is no need for & in the connect() call. Just remove it.