See the Custom Type Example for code. A separate point for your own benefit. Returns the used WebSocket protocol. Actually, they are declared, but in a private section with the macro Q_DISABLE_COPY(). The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. With Q_DECLARE_METATYPE and without qRegisterMetaType: No warning, slot is called With Q_DECLARE_METATYPE and with qRegisterMetaType: No warning, slot is called. 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. 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. g. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. When the plugin is reloaded later, the old declaration still points to the original memory space of the now-unloaded library. void QAbstractSocket:: abort ()Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. Returns true if convert can convert from fromType to toType. [virtual] QAbstractSocket:: ~QAbstractSocket Destroys the socket. QObject can't be copied and all its descendants can't be copied also. The class is used as a helper to marshall types in QVariant and in queued. Well, I certainly overplayed this particular point, but the statement I believe is valid in principle. In my module tests, I turn the card up and down, and can verify that the number of signals are increasing using QSignalSpy. 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 (). This is not the case, since the following succeeded: @QMetaType::type("MyClass"); // success@. 0. void Message:: registerMetaType {qRegisterMetaType < Message >. 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(). EDIT: When you convert your class to QVariant it uses a. 4. 0. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. Q_DECLARE_METATYPE(TYPEDEF) Q_DECLARE_METATYPE(TYPEDEF) mainwindow. You may have to register before you can post: click the register link above to proceed. I think it would be great if we could run requests in a QThread, but right now it's not possible because the r. Output:Additionally Q_DECLARE_METATYPE and qRegisterMetaType are not purposed to be used for QObject derived classes. Now you have a valid QObject. Call qRegisterMetaType () to make type available to non-template based. 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. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. 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. There's no such thing as a "const reference" because references are always const -- you can't reseat them. I want to use drag-and-drop to drag a QTreeWidgetItem that has std::shared_ptr user data. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. I tried and it looks like it's possible to register an enum type with Q_DECLARE_METATYPE or qRegisterMetaType and use it the same way. The default access for a class is private, so that Container* data(); declares a private member function, but it looks like you expect it to be public. 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. You may have to register before you can post: click the register link above to proceed. e. When the plugin is reloaded later, the old declaration still points to the original memory space of the now-unloaded library. QtCore. However, if you want to use a type in a pure runtime context, for example in a QML document, the Qt runtime doesn't know the type declared with Q_DECLARE_METATYPE. QVariant’s operator== now uses QMetaType::equals for the comparison. 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(). But I really would like to know the correct way to solve this problem; one where it is not possible to modify the template classes. 0. 1. Jun 13, 2021 at 19:37. h instead ofQVariant x2; x2. Workaround: use a class. 2. cpp. QLocalSocket. With Q_DECLARE_METATYPE and without qRegisterMetaType: No warning, slot is called With Q_DECLARE_METATYPE and with qRegisterMetaType: No warning, slot is called. Re: Qt warning of type conversion already registered Originally. " Yet types like QVariantMap are themself typedefs. qRegisterMetaType you'll need if creating objects by class name dynamically, and it seems for queued connections,. S 1 Reply Last reply Reply Quote 0. There's no need to call qRegisterMetaType that many times, once is enough. Without this reference, it compiles just fine. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. So using qRegisterMetaType () you will just trade Q_ENUM () for Q_DECLARE_METATYPE (). There's no need to call qRegisterMetaType that many times, once is enough. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. An alternative would be to wrap shared_ptr<int> in your own class and implement comparison the way you want. Now you have a valid QObject. 8. Q_DECLARE_METATYPE. To register VideoMeta you need to call qRegisterMetaType<VideoMeta>(). To copy to clipboard, switch view to plain text mode. 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. 2. When I try to simply connect signalslot with such QVector as argument programm tells during run that this metatype should be registered (though QVector, QSharedPointer and class inherited from QObject should be registered automatically. 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 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. Registers the type name . qRegisterMetaType vs. qRegisterMetaType 必须使用该函数的两种情况. What worries me is that. 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. rep file extension, short for Replica. qRegisterMetaType vs. It manages an insane amount of static variables and sets a static global pointer of. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. QMetaType::type () returns the same ID as qMetaTypeId (), but does a lookup at runtime based on the name of the type. I have registered an enumeration type "ClefType" within my header file - this enum is registered with the MetaObject system using the Q_DECLARE_METATYPE and Q_ENUMS macros. Otherwise your signals and slots connected used the old mechanism (with macros SIGNAL and SLOT) that require queueing of the parameters won't know how to do so. 1. Posted by Unknown at 2:06 AM. Using Q_ENUM () allows you to retrieve at run-time the name of an enum value: Q_GADGET makes a class member, staticMetaObject, available. I need to call the Q_DECLARE_METATYPE() to pass the smart pointer. your custom type definition. I haven't used that module yet but one thing you should do is remove the string argument from your qRegisterMetaType calls. See also. The object it returns should also be a member of the factory class. complains that the metatype isn't registered. the type name must be specified without the class, as in. I want to use my objects as QVariants and for queued connections. By the way, Qt 4. 0. See also Thread Support in Qt, QObject::connect(), qRegisterMetaType(), and Q_DECLARE_METATYPE(). 12. Alt. To enable creation of objects at run-time, call the qRegisterMetaType() template function to register it with the meta-object system. Also Q_DECLARE_METATYPE does not register a type, but declares it. The logical equivalent of a const T &r (reference to const T) is a const T * const p (const pointer to const T). // But the split allows to. There is no way to add support for more of these value types like std::string (*). That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. 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. h" class Context : public QObject { Q_OBJECT Q_PROPERTY (MyGadget* gadget READ gadget CONSTANT) public: explicit Context () : QObject {nullptr} { } MyGadget* gadget () { return &_gadget; } private. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. When these files are processed by repc, repc generates both Source and Replica header files. QLocalSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. (Make sure 'QVector<int>' is. This allows us to use the Enum as a custom-type of a QVariant, to pass it between QML and Qt, to use it in synchronous signal-slot connections, and to print the symbolic enums (instead of a magic number) with qDebug(). The object it returns should also be a member of the factory class. This function is useful to register typedefs so they can be used by QMetaProperty, or in QueuedConnections. Type is not registered, please use the Q_DECLARE_METATYPE macro to make it known to Qt's meta-object system. ) I got the hint "expected a declaration" when I tried to use qRegisterMetaType from the global scope in my cpp file. You may have to register before you can post: click the register link above to proceed. Some structure need to be registered to be queued in asynchronous signals using qRegisterMetaType<T>(name), such as signal which passes QVector<int>. I'm using Qt 5. 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. You may have to register before you can post: click the register link above to proceed. x however, the code generated by moc will call qRegisterMetaType for you if moc can determine that the type may be registered as a. PySide6. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. You may have to register before you can post: click the register link above to proceed. 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. Macros Detailed Description The QMetaType class manages named types in the meta-object system. 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. You can register a class pointer as the metatype, though. (Make sure 'MyStruct' is registered using qRegisterMetaType (). e. Sorted by: 1. This object can then be passed from QML to C++ via Q_INVOKABLE. The id is constexpr in the special case of Qt built-in types only. Q_DECLARE_METATYPE, as pointed out by @SingerOfTheFall, would register template based type into QVariant (so it can be retrieved using qvariant_cast<T>()). The Q_DECLARE_METATYPE() macro and qRegisterMetaType() function documentation contain more detailed information about their uses and limitations. Question: Is there a way to check at compile-time if qRegisterMetaType<T> () was called for a custom type T? The custom type T needs to be registered in Qt meta-type system in order to be used in e. ", which suggests it is only for classes and structs. Adding a Q_DECLARE_METATYPE () makes the type known to all template based functions, including QVariant. Connect and share knowledge within a single location that is structured and easy to search. until today. 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. QVariantList , QString (if the list contains exactly one item) Casting between primitive type (int, float, bool etc. Qt is throwing an exception because it doesn't know how to store the shared_ptr onto a QDataStream. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries that are used. qRegisterMetaType<Subclass> ("Subclass") also doesn't work. It was also no big issue to call qRegisterMetaType () automatically. I read a bit and it seems that Q_DECLARE_SMART_POINTER_METATYPE is supposed to allow this to work. 7. Assuming base and derived are Q_GADGETs you want to get a static member. 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. Call qRegisterMetaType() to register the data type before you establish the connection. Follow answered Jun 5, 2009 at 15:14. What is(are) the good place(s) to put the qRegisterMetaType call? I obviously don't want any expllicit. I have an application that requires use of both Qt 3D and the QCustomPlot library. I tried to write one, but I failed. The class is used to send arguments over D-Bus to remote applications and to receive them back. h. See also isRegistered () and Q_DECLARE_METATYPE (). Make sure you call it from within a method. 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. See also state() and Creating Custom Qt Types. qRegisterMetaType vs. 步骤： (以自定义MyDataType类型为例）. Sorted by: 1. 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. 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. qRegisterMetaType vs. 基本理解. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. 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. qRegisterMetaType vs. I placed Q_DECLARE_METATYPE (DataPoint) after the class definition. I want to use drag-and-drop to drag a QTreeWidgetItem that has std::shared_ptr user data. 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. First of all you need to declare your custom object for Qt metatype system. 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. But this is all useless if you are not using templates. // - in a header: // - define a specialization of this template calling an out-of. As a workaround, I'm using QVariantMap instead of std::map. Even though we do not intend. Mixing doesn't work but if you always use one or the other it works. So, if you had a custom type FooType, you'd put the Q_DECLARE_METATYPE directly after the declaration, and in. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. Obviously then you would not do registerComparator (). 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. 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。. Avoid having to qRegisterMetaType (pointer vs reference), concern about const. To achieve this you need Q_DECLARE_METATYPE macro and qRegisterMetaType () function. Consider the specific case of qRegisterMetaType. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. To register a type, it must be declared as a meta-type with the Q_DECLARE_METATYPE() macro, and then registered as in the following example:. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. Jul 9, 2017 at 21:51. This also makes the type available for queued. Q_DECLARE_METATYPE. 0. 3. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. cpp. fromValue <QList<double> > ( x1); To copy to clipboard, switch view to plain text mode. 4 which does not support all C++11 features. 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. It associates a type name to a type so that it can be created and destructed dynamically at run-time. Share Improve this answer Follow answered Jul 23, 2014 at 15:37. . Q_DECLARE_METATYPE与qRegisterMetaType学习. You should use Q_DECLARE_METATYPE macro for this. 1 Answer. Q_DECLARE_META_TYPE (Fruit) and qRegisterMetaType were redundant: #define PluginInterface_iid "pluginInterface" Q_DECLARE_INTERFACE (PluginInterface, PluginInterface_iid) //Actual plugin implementing PluginInterface class. // copiable, C++98 brace-initializable, etc. Inheritance diagram of PySide6. I have created an qt bugticket hoping the documentation will be extended. Q_GADGET makes a class member, staticMetaObject, available. It does not say anything about registering the type. So my first idea:. Share. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. h in the translation unit where you have that line. 1. 2. 0 and have problems registering my own class as a QMetaType. by using qRegisterMetaType(). You may have to register before you can post: click the register link above to proceed. You may have to register before you can post: click the register link above to proceed. QMetaType Synopsis Functions def __eq__ (b). Some structure need to be registered to be queued in asynchronous signals using qRegisterMetaType<T>(name), such as signal which passes QVector<int>. There's also no need for that typedef, it only makes the code less readable. 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. Here my test code and example:但是如何传递一个程序员自定义的结构体？ 1）在定义结构体之后，要调用Q_DECLARE_METATYPE，向QT声明这个结构体 2）在main. So in your case you need to declare. The. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. There's no such thing as a "const reference" because references are always const -- you can't reseat them. In fact, all Qt classes derived from QObject (direct or indirect) use this macro to declare their copy constructor and assignment operator to be private. Yes, templated types can be used in Qt signal/slots. Declare new types with Q_DECLARE_METATYPE () to make them available to. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. . Q_DECLARE_METATYPE (T) requires the type T to be default-constructable, copiable and destructable. Execute qRegisterMetaType<QItemSelection> (); before it is used as such, e. If the pointer stored in the QVariant can be qobject_cast to T, then that result is returned. I thought there was a bug with QMetaType or Q_DECLARE_METATYPE. before saveload operation would happen. I just found multiple examples showing the usage of Q_ENUM and Q_ENUMS and looking into the definition of Q_ENUM showed me that it includes Q_ENUMS and other definitions. You should use qmlRegisterType function for that. See also. This replaces the now-deprecated Q_ENUMS and will automatically register the metatype. # In the class MainWindow declaration #ifndef Q_MOC_RUN # define the tag text as empty,. 4 and it seems to work. QtCore. The ENUM type. 文章目录 Q_DECLARE_METATYPE qRegisterMetaType Q_DECLARE_METATYPE 使用Q_DECLARE_METATYPE标记自定义类型，可以让QMetaType查询到类型，也可以让QVariant识别。 qRegisterMetaType 在main函数中使用qRegisterMetaType注册自定义类型到元对象系统中,可在跨线程的信号槽中进行参数传递。I'm using Qt5 and qRegisterMetaType is not documented anymore, so I'm not sure if it's deprecated. To register. 2. Detailed Description. Any class or struct that has a public default constructor, a public copy constructor, and a public destructor can be registered. Using the macro directly turned out to be impossible. Q_DECLARE_METATYPE vs qRegisterMetaType for non global namespace classes. However Q_DECLARE_METATYPE () is a bit more complicated. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. It is more or less explained in the manual for int qRegisterMetaType (const char *typeName) This function requires that T is a fully defined type at the point where the function is called. Then the TYPE ID is saved in local static vairable metatype_id. In the header, after the class declaration, outside the namespace, I've included. I'm confused by this error, as the documentation states (emphasis mine): Returns the meta type id of type T at compile time. Any class or struct that has a public default constructor, a public copy constructor, and a. 1. [override virtual] bool QAbstractSocket:: waitForBytesWritten (int msecs = 30000) Reimplements: QIODevice::waitForBytesWritten(int. ) summary refs log tree commit diff stats Foo and Foo* are different types and need to be registered separately. The ones I am registering for are mostly structs for storing data and just a few simple classes. // But the split allows to. 11. I have declared all the types with Q_DECLARE_METATYPE, Q_OBJECT and the properties with Q_PROPERTY with the proper getters and setters. What worries me is that. Q_DECLARE_METATYPE(MyClass*); That's how Qt handles it with QObject and QWidget. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. I however have a scenario where I want to declare such an object in qml and transmit it to the c++. As a workaround, I'm using QVariantMap instead of std::map. 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. Any class or struct that has a public default constructor, a public copy constructor, and a. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. F. To make the custom type. wysota. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. I have a problem with a class that exchanges data using TCP/IP socket. Consider the specific case of qRegisterMetaType. 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. It will return the same result if it was called before. There's also no need for that typedef, it only makes the code less readable. The class is used as a helper to marshall types in QVariant and in queued. It is not safe to make a QObject's copy constructor public. In Qt, you can declare a variable in two ways: 1. That would allow you to use. For pointer types, it also requires that the pointed to type is fully defined. {. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. The "traditional" way of doing this is to convert each element to a QVariant, and pass collection as a QVariantList. Use Q_DECLARE_OPAQUE_POINTER () to be able to register pointers to forward. But I really would like to know the correct way to solve this problem; one where it is not possible to modify. There's no need to call qRegisterMetaType that many times, once is enough. Also you may need to use qRegisterMetaType function. [virtual] QLocalSocket:: ~QLocalSocket Destroys the socket, closing the connection if necessary. Thus you need to use the runtime check QMetaType::type (). But this is all useless if you are not using templates. queued connections. I think you need to add an explicit export/import directive to the QT_NAMESPACE macro. Any class or struct that has a public constructor, a public copy constructor, and a public destructor can be registered. I need to call the Q_DECLARE_METATYPE() to pass the smart pointer. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. qRegisterMetaType 必须使用该函数的两种情况. QObject::connect: Cannot queue arguments of type 'MyStruct'. This has been changed, and isNull () now only returns true if the QVariant is empty or contains a nullptr. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. ) QObject::connect: Cannot queue arguments of type 'QVector<int>'. e. It is only useful to the code that follows it, in the same file. Q_DECLARE_METATYPE(Pkg) and this does not give compile errors, but in my main. But at run time, I got below error:1 Answer. This object can then be passed from QML to C++ via. cpp. See full list on doc. For those who follow. The following should work: Note that you also have to call qRegisterMetaType<MyMpiMessage> (); before you use the function the first time. If \c MyStruct is in a namespace, the Q_DECLARE_METATYPE () macro. To make the custom type generally usable with the signals and slots mechanism, we need to perform some extra work. Note that for enum types, you no not even need to call qRegisterMetaType () in these cases. You have to register your class to Qt meta objects system. Using the following required me to use Q_DECLARE_METATYPE. Couple of points: 1) I would use QScriptEngine::newObject() instead of newQObject() for the namespace 2) I would not use a QObject subclass for the data entry if possible, only the prototype has to be. You may have to register before you can post: click the register link above to proceed. To use the type T in queued signal and slot connections, qRegisterMetaType<T>() must be called before the first connection is established. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. Q_DECLARE_METATYPE accepts objects with public constructor, copy constructor and destructor. } 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. 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. 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. Any class or struct that has a public constructor, a public copy constructor, and a public destructor can be registered. Q_OBJECT derived class, inheritance. Hello Ladies and Gentlemen. The struct is declared in my worker class, which is inside a namespace. 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。. Does your code ever call qRegisterMetatype() or use Q_DECLARE_METATYPE()? 10th November 2014, 05:23 #3. Yes I tried with qRegisterMetaType, it. Hope it. no unexpected garbage. From the docs: int qRegisterMetaType ( const char * typeName ) Registers the type name typeName to the type T. However, it does appear (at least to me) that you're trying to debug a release build of the application. To use the type T in QVariant, using Q_DECLARE_METATYPE() is sufficient. 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. The class in Qt responsible for custom types is QMetaType . qRegisterMetaType<FileNodePointer> ("FileNodePointer"); should be called once (in main, constructor etc. Jun 13, 2021 at 19:37. qRegisterMetaTypeしているにもかかわらずQObject::connectでランタイムエラーが出る場合の回避策. In practice, both the Q_DECLARE_METATYPE() macro and the qRegisterMetaType() template function can be used to register custom types, but qRegisterMetaType() is only required if you need to perform signal-slot communication or need to create and destroy objects of the custom type at run-time. It seems that for a metatype that is a QList<MyClass::MyEnum> I must. ) which are updated by simulation code. Because Foo is not derived from QObject and QVariant only supports polymorphism for QObject -derived types. I am also using some in queued signal and slot connections. My workround was to explicitly cast the enum values to int when passing them onto a function requiring a QVariant type, in my case when adding a QComboBox item, and then casting it back to my enum class type at value retrieval. 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 () <<. multithreaded software and I am getting the warning says: (Make sure 'QVector<int>' is registered using qRegisterMetaType (). Labels: meta system, Meta type, qt. QVariantList MyClass::getFooCollection (void) const { QVariantList list; for (const auto& l: fooCollection_) { list. See the Qt D-Bus Type System page for more information on the type system. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. Q_DECLARE_METATYPE (std::string) Quoting Qt Doc. hpp which is included in Class1. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. Q_DECLARE_METATYPE(MyObject*) somewhere in your code. e. There's no need to call qRegisterMetaType that many times, once is enough. 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. The QMetaType class manages named types in the meta-object system. This won't work because you can't use qMetaTypeId<> () before Q_DECLARE_METATYPE<>. I guess it's the qRegisterMetaType () call itself that's missing.