Cannot queue arguments of type...

[jsulm]

@Engelard Actually from my own praxis I don't see long long used really often (and I guess this is the reason why this type isn't registered by default). In most cases a simple int is enough. Do you really need long long?

[Engelard]

@dheerendra

There is quite nothing to show really
In Header:

Q_DECLARE_METATYPE(signed long long)

CPP file(in constructor):

qRegisterMetaType<signed long long>();

@jsulm if such type would be unnecessary - it would not exist, i do need it because of big whole numbers which billions.

[dheerendra]

Try. qRegisterMetaType<signed long long>("signed long long");
Check the complete example in my git repository

[Engelard]

@dheerendra said in Cannot queue arguments of type...:

Try. qRegisterMetaType<signed long long>("signed long long");

That is correct answer. But in previous topic someone told me that "leave parentheses empty"))

P.S. i found that it working without macro, so only qRegisterMetaType<signed long long>("signed long long"); is enough

[jsulm]

@Engelard said in Cannot queue arguments of type...:

if such type would be unnecessary - it would not exist

Where did I say it is unnecessary?!
Please stay objective!

[dheerendra]

@Engelard said in Cannot queue arguments of type...:

P.S. i found that it working without macro, so only qRegisterMetaType<signed long long>("signed long long"); is enough

hmmm. I did not see any body suggesting like this. Everybody suggested to use the qRegisterMetaType. I was suspecting the way you have done. Hence i asked the code.

[SGaist]

@Engelard said in Cannot queue arguments of type...:

That is correct answer. But in previous topic someone told me that "leave parentheses empty"))

That someone explained you why as stated in the documentation of qRegisterMetatype.

[dheerendra]

Now your issue is fixed, you can move the issue to SOLVED state. It helps others.

[Savitha]

Hi All,

I know the solution has been provided to this problem but it is not working for me.

Here is my code,

Class2.hpp
void slot_ofClass2(quint32 &p_Result, QVector<quint32> &p_Values,
Error& p_error);

Class1.hpp
void signal_fromClass1(quint32& p_Result, QVector<quint32>& p_Values,
Error& p_error);

Class1.cpp

    QObject::connect(this, &Class1::signal_fromClass1,
            loc_class2Obj.data(), &Class2::slot_ofClass2,
            Qt::QueuedConnection);

I have added Q_DECLARE_METATYPE(quint32) in Class2.hpp which is included in Class1.hpp and
qRegisterMetaType<quint32>("quint32"); in both the Constructors of Class1 and Class2.

It is still giving the error"QObject::connect: Cannot queue arguments of type 'quint32&'
(Make sure 'quint32&' is registered using qRegisterMetaType().)"

What am I missing?

[JonB]

@Savitha
I don't know anything about QML/registering meta types, so no point quizzing me further, but looking at the error message and your signal/slot parameters you have registered quint32 but your methods require quint32&. With QML/register meta-type maybe it cannot go from quint32 to quint32&? If so, either register quint32& or change your parameters to quint32 to see if that works? There is little point in passing integer-types as references anyway. [Whoops, I didn't realize you are changing the value.]

[Savitha]

@JonB Thank you for the reply.
If I change my parameters to quint32 it connects to the slot. But my slot_ofClass2 is updating these values which I will be handling in Class1 so I need quint32&.

If I try Q_DECLARE_METATYPE(quint32&) it gives error: 'type name' declared as a pointer to a reference of type 'quint32 &' (aka 'unsigned int &')
and qRegisterMetaType<quint32&>("quint32&"); gives error: no matching function for call to 'qRegisterMetaType<quint32&>(const char [9], quint32*)'

Any solution to handle this problem with references?

I have seen an example with (QString const& s) as a parameter and this works without having to register it as MetaType. So is there any workaround?

[JonB]

@Savitha
Did you try Q_DECLARE_METATYPE(quint32) as well as Q_DECLARE_METATYPE(quint32&)? Other than that you will have to await someone who knows about this.

[Savitha]

@JonB Yes, I tried both together and it gave error for qRegisterMetaType<quint32&>("quint32&");

For now, I will emit one more signal from my Class2 and try to catch my results in a slot of Class1.

Thank you @JonB

[Christian Ehrlicher]

A slot can not take non-const references. Especially not when it's a queued connection.