qRegisterMetaType<FileNodePointer> ("FileNodePointer"); should be called once (in main, constructor etc. QObject::connect: Cannot queue arguments of type 'MyStruct'. There's no need to call qRegisterMetaType that many times, once is enough. F. According to the Qt docs for qRegisterMetaType "Any class or struct that has a public default constructor, a public copy constructor, and a public destructor can be registered. ", which suggests it is only for classes and structs. See also. 如果非QMetaType内置类型要. 4. 4. I read a bit and it seems that Q_DECLARE_SMART_POINTER_METATYPE is supposed to allow this to work. multithreaded software and I am getting the warning says: (Make sure 'QVector<int>' is registered using qRegisterMetaType (). 8. Follow answered Jun 5, 2009 at 15:14. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. @Q_DECLARE_METATYPE (std::unique_ptr<Thing>);@. 能猜到原因吗？注意看前面 Q_DECLARE_METATYPE() 代码， 对了。类中的成员函数qt_metatype_id中包含对qRegisterMetaType(typeName)的调用: 这儿就是辗转调用了这个带参数的qRegisterMetaType函数: unregisterType(const char *typeName) 函数的作用是取消自己先前注册的某个metatype类型。That is sad. Quote: bool QVariant::operator==(const QVariant & v) const. Sorted by: 3. I created a. Note: it's also safe to call qRegisterMetaType () multiple times. 如果要使自定义类型或其他非QMetaType内置类型在QVaiant中使用，必须使用该宏。. This results in access violations when Qt. template <typename T> struct QMetaTypeId<Container<T>>. Now, in your registerTypes function, it should be registered like this: qRegisterMetaType<AccReal > ("data::AccReal"); In other words, the typeName string must match exactly the type of the signal argument as it is written there. See also disconnect(), sender(), qRegisterMetaType(), Q_DECLARE_METATYPE(), and Differences between String-Based and. Note that for enum types, you no not even need to call qRegisterMetaType () in these cases. The ones I am registering for are mostly structs for storing data and just a few simple classes. Use it if you want to use it as a global enumerator and then you need to call the meta-type runtime registration from the library, not from the application. After googling this, I found this correspondence, which was only available through a third party archival site as google. // But the split allows to. Read and abide by the Qt Code of Conduct. One of the overloads is a function template that can be used to create an alias for a type and the form is: qRegisterMetaType<Type> ("alias"); That is, it wants to know the type for which you are declaring something. 14 vs 5. Qt is throwing an exception because it doesn't know how to store the shared_ptr onto a QDataStream. . I just tried. Detailed Description. 5 is compiled with GCC 4. Alt. :) QApplication is the root QObject of the program and its full initialization is required before anything can practically be done with anything else. Q_DECLARE_METATYPE(NSP::MyStruct) qRegisterMetaTypeIt associates a type name to a type so that it can be created and destructed dynamically at run-time. Franzk 26 May 2011, 06:59. Declare new types with Q_DECLARE_METATYPE () to make them available to. QtNetwork. From the docs: int qRegisterMetaType ( const char * typeName ) Registers the type name typeName to the type T. } But you'll most likely need to abstract the Q_DECL_EXPORT part so it is a Q_DECL_IMPORT in right circumstances, as described in Creating Shared Libraries. Also, to use type T with the QObject::property () API, qRegisterMetaType () must be. This also makes the type available for queued. That was it for Q_DECLARE_METATYPE, but you would still need to call qRegisterMetaType to use these type in a Q_PROPERTY or as a parameter in a signal/slot queued connection. qRegisterMetaType<FileNodePointer> ("FileNodePointer"); should be called once (in main, constructor etc. Returns the internal ID used by QMetaType. nyaruko. Normally, you would only register the pointer form if your class cannot be copied, as in the case of QObject and derivatives, but. said, try to directly pass shared_ptr with your signal/slots. First of all you need to declare your custom object for Qt metatype system. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. Q_DECLARE_OPAQUE_POINTER (PointerType) This macro enables pointers to forward-declared types (PointerType) to be registered with QMetaType using either Q_DECLARE_METATYPE() or qRegisterMetaType(). 手册中告诉我们，执行这个的时候，模板参数T必须用 Q_DECLARE_METATYPE() 声明过 能猜到原因吗？注意看前面 Q_DECLARE_METATYPE() 代码， 对了。类中的成员函数qt_metatype_id中包含对qRegisterMetaType(typeName)的调用 这儿就是辗转调用了这个带参数. So using qRegisterMetaType () you will just trade Q_ENUM () for Q_DECLARE_METATYPE (). There's also no need for that typedef, it only makes the code less readable. 14. Trying to register std::map<non_template_type_1,non_template_type_2> with Q_DECLARE_METATYPE() results in compilation failure and apparently is not supported. We will still need to register it with the meta-object system at run-time by calling the qRegisterMetaType () template function before we make any signal-slot connections that use this type. This function returns the Qt meta type id for the type (the same value that is returned from qRegisterMetaType()). ) summary refs log tree commit diff stats Foo and Foo* are different types and need to be registered separately. The reason to need this is usually that Q_PROPERTY is used with a metatype which is not built-in (types such as int and QString are built-in and don’t. Data Type Conversion Between QML and C++. You have to register your class to Qt meta objects system. canConvert<x> (); } and. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. In the header, after the class declaration, outside the namespace, I've included. cruz Hello, To be completely candid, I haven't used GDB remotely and I'm certainly not so intimate with it for the log to speak to me much. int videoSourceMetaTypeId = qRegisterMetaType< VideoSource > ();Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. After googling this, I found this correspondence, which was only available through a third party archival site as google. I am also using some in queued signal and slot connections. QVariant::fromValue () returns a QVariant. qRegisterMetaType vs. cpp I have to do: qRegisterMetaType<Pkg>("Pkg"); and this does not give errors too, but when I try to create a QVariant(Pkg) I get lots of errors like:cardio63 26 Jan 2016, 10:19. This object can then be passed from QML to C++ via Q_INVOKABLE. Call qRegisterMetaType () to make type available to non-template based. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. Has anyone else encountered this?See also qRegisterMetaType(). // This primary template calls the -Implementation, like all other specialisations should. 2. The Q_DECLARE_METATYPE() macro and qRegisterMetaType() function documentation contain more detailed information about their uses and limitations. 2、在类型定义完成后，加入声明：Q_DECLARE_METATYPE (MyDataType); 3、在main ()函数中. If you need the functionality provided by Q_DECLARE_METATYPE, you will have to use it. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. It will return the same result if it was called before. Our first stop for registrations always is the macro Q_DECLARE_METATYPE. To make the custom. Now I want to read this property with Qt's meta object system. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. Q_DECLARE_METATYPE. In general, you can only export two kinds of C++ types to QML: QObject-derived classes and some build-in value types, see this documentation page. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. Output:Additionally Q_DECLARE_METATYPE and qRegisterMetaType are not purposed to be used for QObject derived classes. See also state() and Creating Custom Qt Types. Qt Code: Switch view. The "traditional" way of doing this is to convert each element to a QVariant, and pass collection as a QVariantList. There's also no need for that typedef, it only makes the code less readable. J. 4] QString QWebSocket:: subprotocol const. I need to call the Q_DECLARE_METATYPE() to pass the smart pointer. QtCore. Avoid having to qRegisterMetaType (pointer. until today. g. 6. @Daddedebad As @Bonnie says qRegisterMetaType. Assuming base and derived are Q_GADGETs you want to get a static member. So, you don't want 'Widget' to be a metatype, you want 'Widget*' to be a metatype so that you can put a Widget* in a QVariant for example. 总之，有时候，我们多么希望信号能发送自定义数据类型。. complains that the metatype isn't registered. However Q_DECLARE_METATYPE () is a bit more complicated. Can it be Done for a Custom Type? If you really need the qMetatypeId<Type>() to be constexpr, you have to take the responsibility for making it so by specializing struct QMetaTypeId<Type> (or. If you want to pass IBase * between different threads, you need to register class with qRegisterMetaType<IBase *> () call; It is bad practice to pass pointers throught singals, because it is hard to control lifetime of passed objects. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. When using signals and slots with multiple threads, see Signals and Slots Across Threads. Note that you are technically lying to the meta type system. Update. It associates a type name to a type so that it can be created and destructed dynamically at run-time. Note that if you intend to use the type in queued signal and slot connections or in QObject 's property system, you also have to call qRegisterMetaType () since the names are resolved at runtime. Note that if you intend to use the type in queued signal and slot connections or in QObject 's property system, you also have to call qRegisterMetaType () since the names are resolved at runtime. This worked very well. 1. QtCore. Step 2 (meta type Declare macro), if needed, describe your custom type/class to things like QVariant, QDebug and other "support" systems used everywhere on QObjects. ) I got the hint "expected a declaration" when I tried to use qRegisterMetaType from the global scope in my cpp file. queued connections. When I emit a signal, then I get next error to the output stream:. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. You can create Q_GADGETS in QML using a C++ factory object registered to be accessible in QML, and a Q_INVOKABLE function in this factory which returns an instance of the Q_GADGET object. The class is used as a helper to marshall types in QVariant and in queued. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries that are used. Join Date Mar 2010 Posts 69 Thanks 8 Thanked 1 Time in 1 Post Qt products Platforms} Q_DECLARE_METATYPE(Topic) In main, I have included this: qRegisterMetaType<Topic>("Topic"); When propagating these elements from c++ to QML, everything is working. However, as you need the type to be. There's no such thing as a "const reference" because references are always const -- you can't reseat them. Make sure you call it from within a method. See the Custom Type Example for code that demonstrates this. I have created an qt bugticket hoping the documentation will be extended. 2. QMetaType::type () is a bit slower, but compilation succeeds if a type is not registered. This version of the function is to register alias types. This won't work because you can't use qMetaTypeId<> () before Q_DECLARE_METATYPE<>. To make the type known to this class, we invoke the Q_DECLARE_METATYPE() macro on the class in the header file where it is defined: Q_DECLARE_METATYPE (Message). To use the type T in queued signal and slot connections, qRegisterMetaType () must be called before the first connection is established. 4 which does not support all C++11 features. Does your code ever call qRegisterMetatype() or use Q_DECLARE_METATYPE()? 10th November 2014, 05:23 #3. QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_REGISTER_METATYPE() and qRegisterMetaType(). uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. Normally, you would only register the pointer form if your class cannot be copied, as in the case of QObject and derivatives, but. We all have started by asking questions. Q_DECLARE_METATYPE vs qRegisterMetaType for non global namespace classes. I think you need to add an explicit export/import directive to the QT_NAMESPACE macro. Here you can see that the macro expands to nothing. g. Note that you are technically lying to the meta type system. Declare new types with Q_DECLARE_METATYPE () to make them available to QVariant and other template. Detailed Description. I'm using Qt 5. Q_DECLARE_METATYPE. To start viewing messages, select the forum that you want to visit from the selection below. qRegisterMetaType 必须使用该函数的两种情况. 1 Answer Sorted by: 21 Objects are copied when put into a QVariant, but QObject derived classes cannot be copied, so the solution is to use a pointer to your. As you have already found out, you must use Q_DECLARE_METATYPE to make the type known to Qt. So in your case you need to declare. I want to use my objects as QVariants and for queued connections. Labels: meta system, Meta type, qt. Any class or struct that has a public default constructor, a public copy. Read and abide by the Qt Code of Conduct. Call qRegisterMetaType() to register the data type before you establish the connection. But this is all useless if you are not using templates. 2 Answers. 1）引入头文件：#include<QMetaType>. For those who follow. the type name must be specified without the class, as in. 基本理解. Registers the type name . The documenation of this macro gives. To start viewing messages, select the forum that you want to visit from the selection below. Q_DECLARE_METATYPE. All I want to do is be able to convert this to a byte array in order to send on a socket, and get the object back (deserialize) on the other end. Note that if you intend to use the type in queued signal and slot connections or in QObject's property system, you also have to call qRegisterMetaType() since the names are resolved at runtime. type() typeName() PySide6. There's no need to call qRegisterMetaType that many times, once is enough. Read and abide by the Qt Code of Conduct. // to be declared somewhere Q_DECLARE_METATYPE(std::string); // to be invoked at the beginning of program qRegisterMetaType<std::string>(); Without type registration Qt doesn't know how to do. QList<AnotherObject*> has of course been registered with Q_DECLARE_METATYPE and qRegisterMetaType(). Even though we do not intend to use the type with QVariant in this example, it is good practice to also declare the new type with Q_DECLARE_METATYPE(). 4] QString QWebSocket:: subprotocol const. qRegisterMetaType vs. By convention, these files are given a . As said in int qRegisterMetaType () documentation: To use the type T in QVariant, using Q_DECLARE_METATYPE () is sufficient. Using the macro directly turned out to be impossible. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. You pass around pointers instead. PySide6. There's no compile time error, but when I run. Re: Q_DECLARE_METATYPE vs qRegisterMetaType for non global namespace classes (QTest) The reason for this behavior might be caused by the fact that runtime signal/slot connections are checked by string manipulation - both Q_DECLARE_METATYPE, SIGNAL, SLOT macros and 'moc' are (among other things) converting type-names to text and pass it along. See also. So I played around, copied the original macro and adapted it a bit: @. JulienMaille @kshegunov last edited by JulienMaille . And once all of them are updated I'd like the Context object to inform QML to update the view. You can use Q_DECLARE_METATYPE(Widget*) but it is not needed as of Qt. You may have to register before you can post: click the register link above to proceed. before saveload operation would happen. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. As a workaround you can call the Q_DECLARE_METATYPE macro from the implementation files that need it instead of calling it from the header files, or as the documentation suggests, call it from private headers in each library. Once they're known you can use them, but you can't create them on the QML side. rep file extension, short for Replica. With Q_DECLARE_METATYPE and without qRegisterMetaType: No warning, slot is called With Q_DECLARE_METATYPE and with qRegisterMetaType: No warning, slot is called. . Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. Note that if you intend to use the type in queued signal and slot connections or in QObject's property system, you also have to call qRegisterMetaType() since the names are resolved at runtime. I have a const pointer to a class derived from qobject and want to put into QVariant like below: QVariant::fromValue(objectPointer) I have declared the meta type of derived class using: Q_DECLARE_METATYPE(const QDrivedClass *) in the header file (. Your Matrix type is not copiable, thus you can't use Q_DECLARE_METATYPE on it. Share. It associates a type name to a type so that it can be created and destructed dynamically at run-time. So using a QString as the type of a Q_PROPERTY only works because it has special built-in support in the QML engine. I'm trying to use custom classes in QAbstractListModel, and the Q_DECLARE_METATYPE doesn't work at all! To test where the problem is, I've simplified the code as the following: #include <QMetaType> #include <QVariant> #include <QDebug> typedef int x; Q_DECLARE_METATYPE (x) void main () { QVariant v; qDebug () <<. Q_DECLARE_METATYPE, as pointed out by @SingerOfTheFall, would register template based type into QVariant (so it can be retrieved using qvariant_cast<T>()). It is often easier and cleaner to define an ENUM inside a class (see ENUM), but if you need a standalone enum type, using the ENUM keyword outside of a class definition can be. QMetaType registerNormalizedTypedef normalizedTypeName, type: metaType ); return. cpp. Does your code ever call qRegisterMetatype() or use Q_DECLARE_METATYPE()? 10th November 2014, 06:23 #3. To copy to clipboard, switch view to plain text mode. ), or any other callable, cannot declare a type for use outside of the call site. 0. 3. . } But you'll most likely need to abstract the Q_DECL_EXPORT part so it is a Q_DECL_IMPORT in right circumstances, as described in Creating Shared Libraries. Any class or struct that has a public constructor, a public copy constructor, and a public destructor can be registered. You can also use QMetaEnum::fromType() to get the QMetaEnum. I tested your code on Qt 5. I think you should consider making the signal/slot parameter be const QVector<int>& dataSet. This function was introduced in Qt 6. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. ) I got the hint "expected a declaration" when I tried to use qRegisterMetaType from the global scope in my cpp file. Read and abide by the Qt Code of Conduct. jsulm Lifetime Qt Champion @shivaVMC last edited by . by using qRegisterMetaType(). The Q_DECLARE_METATYPE () macro also makes it possible for these values to be used as arguments to signals, but only in direct signal-slot connections. Hello Ladies and Gentlemen. In my module tests, I turn the card up and down, and can verify that the number of signals are increasing using QSignalSpy. The object it returns should also be a member of the factory class. In Qt, you can declare a variable in two ways: 1. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. To make the type known to this class, we invoke the Q_DECLARE_METATYPE() macro on the class in the header file where it is defined: Q_DECLARE_METATYPE (Message). struct StandardData { int EmpId; QString Name; }; Q_DECLARE_METATYPE (StandardData) Additionally, you might need to call qRegisterMetaType. When these files are processed by repc, repc generates both Source and Replica header files. Share Improve this answer Follow answered Jul 23, 2014 at 15:37. Use Q_DECLARE_OPAQUE_POINTER () to be able to register pointers to forward. Yes, templated types can be used in Qt signal/slots. Q_DECLARE_METATYPE. QMetaType. Qt is throwing an exception because it doesn't know how to store the shared_ptr onto a QDataStream. I tried with and without the qRegisterMetaType<Schedule::TimePairMap>(), with and without Q_DECLARE_METATYPE(Schedule::TimePairMap). It was also no big issue to call qRegisterMetaType () automatically. In the example's Message class, a static method is included to do this. Share Improve this answerWe will still need to register it with the meta-object system at run-time by calling the qRegisterMetaType() template function before we make any signal-slot connections that use this type. The Custom Type and Queued Custom Type examples show how to implement a custom type with the features outlined in this document. 8. To start viewing messages, select the forum that you want to visit from the selection below. e. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. Declare new types with Q_DECLARE_METATYPE () to make them available. 0. 14. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. To use the type T in QVariant, using Q_DECLARE_METATYPE() is sufficient. Q&A for work. QMetaType::type () is a bit slower, but compilation succeeds if a type is not registered. But because QUuid stores its content as a QByteArray which is already supported by QVariant, you. The following should work: Note that you also have to call qRegisterMetaType<MyMpiMessage> (); before you use the function the first time. This function was introduced in Qt 6. Secondly, your linker (MSVC) complains that it can't find the metaObject for your ErrorHandler enum, which is normal as it is not exported from the. Secondly, your linker (MSVC) complains that it can't find the metaObject for your ErrorHandler enum, which is normal as it is not exported from the. But I can't see a method to insert myClass into. Any class or struct that has a public default constructor, a public copy. However, when attempting to compile QCustomPlot in a project using "QT += 3dinput" in its . uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. The third without Q_DECLARE_METATYPE. The. What you made is a const pointer to a non-const T; but top-level consts in function signatures are not part of the function. The Custom Type, Custom Type Sending and Queued Custom Type examples show how to implement a custom type with the features outlined in this document. To use the type T in queued signal and slot connections, qRegisterMetaType<T>() must be called before the first connection is established. The problem of owner ship of the memory is avoided. The correct syntax is Q_DECLARE_METATYPE (std::string) without the ;. genC last edited by . cpp. Note that if you intend to use the type in queued signal and slot connections or in QObject 's property system, you also have to call qRegisterMetaType () since the names are resolved at runtime. If you want both, then register both. Greetings. statement to the header file containing. {. @user6556709 I've added both of those, and it does compile now, but the string is just being default initialized to "" when I call value<T>() and there's a red line under Q_DECLARE_METATYPE that says no instance of overloaded function "qRegisterMetaType" matches the argument list, argument types are: (const char [12],. Here’s the list of what changed: QVariant used to forward isNull () calls to its contained type – but only for a limited set of Qt’s own types. no unexpected garbage. To use the type T in queued signal and slot connections, qRegisterMetaType () must be called before the first connection is established. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. This function was introduced in Qt 4. . I tried to write one, but I failed. Q_DECLARE_METATYPE与qRegisterMetaType学习. I meet a qt metatype issue. [virtual] QLocalSocket:: ~QLocalSocket Destroys the socket, closing the connection if necessary. Thus you need to use the runtime check QMetaType::type (). 用qRegisterMetaType对自定义的类型进行注册，就是为了告诉Qt如何去做这些事情。. and Q_DECLARE_METATYPE uses qRegisterMetaType() internally. With Q_DECLARE_METATYPE and without qRegisterMetaType: No warning, slot is called With Q_DECLARE_METATYPE and with qRegisterMetaType: No warning, slot is called. qRegisterMetaType<signed long long>() - do nothing. without providing the Q_DECLARE_METATYPE macro in the class header, but one could provide a macro where registration is automatically performed (more or less along with meta type declaration). You could also Q_DECLARE_METATYPE to register your custom type and then use qMetaTypeId() to get the metaType id. Connect and share knowledge within a single location that is structured and easy to search. This function was introduced in Qt 4. QMetaType. When the plugin is reloaded later, the old declaration still points to the original memory space of the now-unloaded library. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. This requires the exchanged data to be of a type that is recognizable by the engine. As you already have a typedef for your type, you can simply use Q_DECLARE_METATYPE as in the following example: #include <QtCore> template <typename T> struct Proxy { T data; }; typedef Proxy<QImage> TrayType; Q_DECLARE_METATYPE (TrayType) class Donor : public QObject { Q_OBJECT public. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. Qt Remote Objects Compiler. e. QVariant x2 = QVariant::fromValue( x1); To copy to clipboard, switch view to plain text mode. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. The macro will register your variable with the Qt Meta-Object System, which will allow you to. Make a typedef for QSharedPointer<UserDataType>, and use both Q_DECLARE_METATYPE as well as qRegisterMetaType () to register it for use. Any errors from Qt's metatype systems are usually due to MOC (the "meta-object compiler"), which reads your header files and generates a "moc" file with metatype information for every class where the Q_OBJECT macro is declared. 1. . You can register a class pointer as the metatype, though. Add qRegisterMetaType and qDBusRegisterMetaType calls to enable the framework to work with the custom type. To make the type known to this class, we invoke the Q_DECLARE_METATYPE () macro on the class in the header file where it is defined: Q_DECLARE_METATYPE(Message); This now makes it possible for Message values to be stored in QVariant objects and retrieved later. See the Qt D-Bus Type System page for more information on the type system. We will still need to register it with the meta-object system at run-time by calling the qRegisterMetaType() template function before we make any signal-slot connections that use this type. What worries me is that. A separate point for your own benefit. Q_DECLARE_METATYPE only registers a type in meta type system. That's created by this macro. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. // copiable, C++98 brace-initializable, etc. From the docs: int qRegisterMetaType ( const char * typeName ) Registers the type name typeName to the type T. Note: it's also safe to call qRegisterMetaType () multiple times. It's not enough to get reflection features out of a type this way (it does not create a QMetaObject), so for the thing to be useful at all you need at least Q_GADGET in both base and derived classes. Please note that I do not use Q_DECLARE_METATYPE on purpose because I don't actually need its features (QVariant expansion) right now. To start viewing messages, select the forum that you want to visit from the selection below. Passing across threads (queued connection) will copy the QVector in either case, but the const will remind you that you cannot alter the original QVector in. Connect and share knowledge within a single location that is structured and easy to search. void QAbstractSocket:: abort ()2 Answers. The struct is declared in my worker class, which is inside a namespace. So in both cases qRegisterMetaType isn't required for the slot to be called and the custom type to be accessible within the slot (i. So in both cases qRegisterMetaType isn't required for the slot to be called and the custom type to be accessible within the slot (i. So I tried declaring the following at end of my worker thread class Q_DECLARE_METATYPE(cv::Mat);. Returns the internal ID used by QMetaType.