I placed Q_DECLARE_METATYPE (DataPoint) after the class definition. QVariant’s operator== now uses QMetaType::equals for the comparison. このケースでも、Q_DECLARE_METATYPE(QSharedPointer<MyObject>)の宣言と、qRegisterMetatype<QSharedPointer<MyObject>>()の呼び出しが必要になる。 上のサンプルでは、同じsignalに対して2回connectを実行している。 The correct syntax is Q_DECLARE_METATYPE (std::string) without the ;. Enum has been moved from outside of the class to inside of it. To make the custom type. I tried to write one, but I failed. QList of Custom Objects. Declare new types with Q_DECLARE_METATYPE () to make them available. 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. I can access the property. qRegisterMetaType usage. Qt5でシグナルの引数としてユーザー定義型を指定する場合は、Q_DECLARE_METATYPEとqRegisterMetaType()を使って方の登録を行う必要がある。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. But I couldn't register the type because it's a QObject and I don't have access to the implementation to change it. Jul 9, 2017 at 21:51. Hope it. Believing an Question from 2010 and the Qt Documentation, the operator==() doesn't work with custom types. w/out GUI module you wouldn't have any of those types available). An alternative would be to wrap shared_ptr<int> in your own class and implement comparison the way you want. You may have to register before you can post: click the register link above to proceed. 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. It manages an insane amount of static variables and sets a static global pointer of. So I don't stream the pointer itself just copy the properties and set them to a new created pointer object. You pass around pointers instead. 1 Answer. Note that you are technically lying to the meta type system. 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 (. Using the macro directly turned out to be impossible. Note that for enum types, you no not even need to call qRegisterMetaType () in these cases. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries that are used. Detailed Description The QMetaType class manages named types in the meta-object system. Also you may need to use qRegisterMetaType function. Call qRegisterMetaType () to make type available to non-template based. As a workaround, I'm using QVariantMap instead of std::map. The id is constexpr in the special case of Qt built-in types only. 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. h" class Context : public QObject { Q_OBJECT Q_PROPERTY (MyGadget* gadget READ gadget CONSTANT) public: explicit Context () : QObject {nullptr} { } MyGadget* gadget () { return &_gadget; } private. 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). type() typeName() PySide6. Q_DECLARE_METATYPE. The QMetaType class manages named types in the meta-object system. The documentation for exposing C++ properties to QML says that: "Note: Do not use typedef or using for Q_PROPERTY types as these will confuse moc. See also state(). In Qt, you can declare a variable in two ways: 1. To copy to clipboard, switch view to plain text mode. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. All Qt Overviews. There's no such thing as a "const reference" because references are always const -- you can't reseat them. This function was introduced in Qt 5. Jun 13, 2021 at 19:37. qRegisterMetaType vs. ", which suggests it is only for classes and structs. Returns the used WebSocket protocol. But there would be no trouble using the QMetaType class or using qRegisterMetaType before creating an instance of QCoreApplication or QApplication. Does your code ever call qRegisterMetatype() or use Q_DECLARE_METATYPE()? 10th November 2014, 05:23 #3. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. Make a typedef for QSharedPointer<UserDataType>, and use both Q_DECLARE_METATYPE as well as qRegisterMetaType () to register it for use. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. g. QMetaType registerNormalizedTypedef normalizedTypeName, type: metaType ); return. From the docs: int qRegisterMetaType ( const char * typeName ) Registers the type name typeName to the type T. I guess it's the qRegisterMetaType () call itself that's missing. 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. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. 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。 and a Context class that holds an instance of MyGadget and exposes a pointer to it to QML via a Q_PROPERTY: #include <QObject> #include "mygadget. To call qRegisterMetaType (), you still need to use Q_DECLARE_METATYPE (). The class in Qt responsible for custom types is QMetaType. If the type was not declared with Q_DECLARE_METATYPE (), compilation will fail. What is(are) the good place(s) to put the qRegisterMetaType call? I obviously don't want any expllicit. So in your case you need to declare. 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. Q_DECLARE_METATYPE与qRegisterMetaType学习. 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. The reasoning is found in the discussion on Identity vs Value on the Qt Object Model page. 0. QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_REGISTER_METATYPE() and qRegisterMetaType(). 0. It associates a type name to a type so that it can be created and destructed dynamically at run-time. The Q_DECLARE_METATYPE() macro and qRegisterMetaType() function documentation contain more detailed information about their uses and limitations. 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. However, as you need the type to be. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. Your Matrix type is not copiable, thus you can't use Q_DECLARE_METATYPE on it. 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 seems that for a metatype that is a QList<MyClass::MyEnum> I must. This function returns the Qt meta type id for the type (the same value that is returned from qRegisterMetaType()). See the Qt D-Bus Type System page for more information on the type system. in a header file and call @qRegisterMetaType<std::unique_ptr<Thing>> ();@ before your signal and slots are used. The class is used as a helper to marshall types in QVariant and in queued. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. container. I also don't want to use qRegisterMetaType, since it is run-time bound. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. This function was introduced in Qt 6. When these files are processed by repc, repc generates both Source and Replica header files. Remember that Q_DECLARE_METATYPE merely defines a specialization of QMetaTypeId for your type. It looks like one can register a type more than once, specifying different typenames, i. multithreaded software and I am getting the warning says: (Make sure 'QVector<int>' is registered using qRegisterMetaType (). (Make sure 'QVector<int>' is. If you need the functionality provided by Q_DECLARE_METATYPE, you will have to use it. Consider the specific case of qRegisterMetaType. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. qt. 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 following should work: Note that you also have to call qRegisterMetaType<MyMpiMessage> (); before you use the function the first time. 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. You don't pass around copies of QObject derived types because it is not copyable. rep file extension, short for Replica. By convention, these files are given a . I however have a scenario where I want to declare such an object in qml and transmit it to the c++. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. QMetaType Synopsis Functions def __eq__ (b). QVariantList , QString (if the list contains exactly one item) Casting between primitive type (int, float, bool etc. Declare new types with Q_DECLARE_METATYPE () to make them available to QVariant and other template-based functions. QtCore. See also. Note that you are technically lying to the meta type system. 8. state() Creating Custom Qt Types. fromValue <QList<double> > ( x1); To copy to clipboard, switch view to plain text mode. 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. Thanks for the suggestion. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. 5 is compiled with GCC 4. Step 1 (mark for MOC), build some QObjects That pattern uses Q_PROPERTY and Q_OBJECT and the MoC tool. This function is useful to register typedefs so they can be used by QMetaProperty, or in QueuedConnections. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. You are looking for the Q_ENUM () macro. However, it does appear (at least to me) that you're trying to debug a release build of the application. Any class or struct that has a public constructor, a public copy constructor, and a public destructor can be registered. Q&A for work. That's created by this macro. 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(). However, when attempting to compile QCustomPlot in a project using "QT += 3dinput" in its . ) I got the hint "expected a declaration" when I tried to use qRegisterMetaType from the global scope in my cpp file. 0. Ah, sorry, I didn't noticed that part. 0. To start viewing messages, select the forum that you want to visit from the selection below. When data values are exchanged between QML and C++, they are converted by the QML engine to have the correct data types as appropriate for use in QML or C++. 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. In the example's Message class, a static method is included to do this. Franzk 26 May 2011, 06:59. I have a problem with a class that exchanges data using TCP/IP socket. QVariant v = QVariant::fromValue<cMyClass>(MyObject); However, as soon as I use Q_DECLARE_METATYPE, I get errors about using a deleted function. 8 and it all went well with a few function changes, except I got QMetaProperty::read: Unable to handle unregistered datatype errors all over. I have an application that requires use of both Qt 3D and the QCustomPlot library. As G. To call qRegisterMetaType (), you still need to use Q_DECLARE_METATYPE (). 4 and it seems to work. Macros Detailed Description The QMetaType class manages named types in the meta-object system. 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. 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. 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. namespace CCS { Q_DECL_EXPORT Q_NAMESPACE. There's no compile time error, but when I run. Q_DECLARE_METATYPE (std::string) Quoting Qt Doc. 该类型必须有公有的 构造、析构、复制构造 函数. You have to register your class to Qt meta objects system. Than I did read this copy constructor of derived QT class and the answer by BЈовић. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. 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. Also Q_DECLARE_METATYPE does not register a type, but declares it. ), or any other callable, cannot declare a type for use outside of the call site. ) What I'm trying to do is send a signal containing two cv::Mat images from a QThread to the main thread, so that I can display the output. The. Then the TYPE ID is saved in local static vairable metatype_id. This object can then be passed from QML to C++ via. 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. 9k 9 34 52. "Custom types used by properties need to be registered using the Q_DECLARE_METATYPE() macro so that their values can be stored in QVariant objects. Some structure need to be registered to be queued in asynchronous signals using qRegisterMetaType<T>(name), such as signal which passes QVector<int>. 1 Answer. Yes, templated types can be used in Qt signal/slots. I simplified the code quite a bit and the problem went away. See also state() and Creating Custom Qt Types. 3. Once they're known you can use them, but you can't create them on the QML side. 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. So I am doing this: Qt Code: Switch view. Please note that I do not use Q_DECLARE_METATYPE on purpose because I don't actually need its features (QVariant expansion) right now. Good workaround: you may register your type with Q_DECLARE_METATYPE ( IBase * ) macro and wrap your variable. Similarly you can create a mutable view of type QAssociativeIterable on any container registered with Q_DECLARE_ASSOCIATIVE_CONTAINER_METATYPE(). QDBusArgument is the central class in the Qt D-Bus type. Original Question. Make your own typedef and do the Q_DECLARE_METATYPE and qRegisterMetatype. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. The logical equivalent of a const T &r (reference to const T) is a const T * const p (const pointer to const T). 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. The QMetaType class manages named types in the meta-object system. The Qt docs make it clear that to use a custom type with Queued Connections, I need to use both Q_DECLARE_METATYPE and qRegisterMetaType. There's no need to call qRegisterMetaType that many times, once is enough. g. 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. But I really would like to know the correct way to solve this problem; one where it is not possible to modify. 被 Q_DECLARE_METATYPEQ 标记的类型可以让Q MetaType 查询到类型，也可以让QVariant识别到。 struct MyStruct { QString name; }; Q_DECLARE_METATYPE(MyStruct) 若对象包含在自定义的命名空间中时，注册时要带上完整的命令空间. I store them in QVariant :. 被 Q_DECLARE_METATYPEQ 标记的类型可以让Q MetaType 查询到类型，也可以让QVariant识别到。 struct MyStruct { QString name; }; Q_DECLARE_METATYPE(MyStruct) 若对象包含在自定义的命名空间中时，注册时要带上完整的命令空间. Current the only supported type info is QML_HAS_ATTACHED_PROPERTIES. So you can call it from your constructor. 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. Our first stop for registrations always is the macro Q_DECLARE_METATYPE. e. I my real world application Context holds a large number of physical quantities (masses, forces, velocities,. To start viewing messages, select the forum that you want to visit from the selection below. Per Qt documentation: To use the type T in QVariant, using Q_DECLARE_METATYPE () is sufficient. To start viewing messages, select the forum that you want to visit from the selection below. You can register a class pointer as the metatype, though. QVariantList MyClass::getFooCollection (void) const { QVariantList list; for (const auto& l: fooCollection_) { list. I'm confused by this error, as the documentation states (emphasis mine): Returns the meta type id of type T at compile time. queued connections. Re: Q_DECLARE_METATYPE problem. I read a bit and it seems that Q_DECLARE_SMART_POINTER_METATYPE is supposed to allow this to work. At the point where I want to read the list, I only care about (and know) the fact that the list contains pointers to objects, which have been derived. [override virtual] bool QAbstractSocket:: waitForBytesWritten (int msecs = 30000) Reimplements: QIODevice::waitForBytesWritten(int. From the QVariant::value documentation: If the QVariant contains a pointer to a type derived from QObject then T may be any QObject type. The application using it does this: typedef QMap<int, int> MyOtherType; Q_DECLARE_METATYPE (MyOtherType) qRegisterMetaType<MyOtherType> (); Now the D-Bus marshaller and demarshaller get registered with the wrong type id. Accessing an enum stored in a QVariant. I'd understood if i want to pass my custom type like struct or so, but it is essential type. Compares this QVariant with v and returns true if they are equal;. J. append (QVariant::fromValue (l)); } return list; } The metatype system declaration and registration you have. You can also use QMetaEnum::fromType() to get the QMetaEnum. Q_DECLARE_METATYPE(TYPEDEF) Q_DECLARE_METATYPE(TYPEDEF) mainwindow. qRegisterMetaType you'll need if creating objects by class name dynamically, and it seems for queued connections,. This object can then be passed from QML to C++ via Q_INVOKABLE. To start viewing messages, select the forum that you want to visit from the selection below. 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. Q_DECLARE_METATYPE is required to store type with QVariant, those two are required to register object's "big three" to manage it as resource and its serialization methods. But this is all useless if you are not using templates. Q_DECLARE_METATYPE QMetaType::type. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. Q_DECLARE_METATYPE与qRegisterMetaType学习. Any class or struct that has a public default constructor, a public copy constructor, and a. 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. Q_DECLARE_METATYPE(MyStruct) Q_DECLARE_METATYPE(MyList) QDBusArgument &operator<<(QDBusArgument &, const MyStruct&);. The following should work: Note that you also have to call qRegisterMetaType<MyMpiMessage> (); before you use the function the first time. You may have to register before you can post: click the register link above to proceed. QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). canConvert<x> (); } and. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. That's created by this macro. Obviously then you would not do registerComparator (). I pass the MyClass pointer to the streaming operator and only stream things like QString, QPointF, etc. QMetaType::type () returns the same ID as qMetaTypeId (), but does a lookup at runtime based on the name of the type. I am also using some in queued signal and slot connections. Using Q_ENUM () allows you to retrieve at run-time the name of an enum value: Q_GADGET makes a class member, staticMetaObject, available. [override virtual] bool QAbstractSocket:: waitForBytesWritten (int msecs = 30000) Reimplements:. 24th July 2010, 09:54 #6. QMetaType registerNormalizedTypedef normalizedTypeName, type: metaType ); return. 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. By convention, these files are given a . Although I'm. I think you need to add an explicit export/import directive to the QT_NAMESPACE macro. QObject can't be copied and all its descendants can't be copied also. 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. Q_DECLARE_META_TYPE (Fruit) and qRegisterMetaType were redundant: #define PluginInterface_iid "pluginInterface" Q_DECLARE_INTERFACE (PluginInterface, PluginInterface_iid) //Actual plugin implementing PluginInterface class. 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. e. To use the type T in QVariant, using Q_DECLARE_METATYPE() is sufficient. This function is typically used together with construct () to perform low-level management of the memory used by a type. From the docs: int qRegisterMetaType ( const char * typeName ) Registers the type name typeName to the type T. h. Yes I tried with qRegisterMetaType, it. 1、自定MyDataType 类型，在这个类型的顶部包含：#include <QMetaType>. 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. The issue here is that Q_OBJECT forbids the copy and assignment constructors. template <typename T> struct QMetaTypeId<Container<T>>. QLocalSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). Returns the metatype of the parameter at the given index. QMetaType::type () is a bit slower, but compilation succeeds if a type is not registered. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. To use the type T in queued signal and slot connections, qRegisterMetaType<T>() must be called before the first connection is established. 如果非QMetaType内置类型要. This has been changed, and isNull () now only returns true if the QVariant is empty or contains a nullptr. 1. " and: "Warning: This function is useful only for registering an alias (typedef) for every other use case Q_DECLARE_METATYPE and qMetaTypeId() should be used instead. 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. on top of main. I just tried. [virtual] QLocalSocket:: ~QLocalSocket Destroys the socket, closing the connection if necessary. @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],. Even though we do not intend. Good workaround: you may register your type with Q_DECLARE_METATYPE ( IBase * ) macro and wrap your. 4. 14. [virtual] QAbstractSocket:: ~QAbstractSocket Destroys the socket. What is(are) the good place(s) to put the qRegisterMetaType call? I obviously don't want any expllicit initialization. Thus you need to use the runtime check QMetaType::type (). The reasoning is found in the. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries that are used. This requires the exchanged data to be of a type that is recognizable by the engine. You can also use QMetaEnum::fromType() to get the QMetaEnum. Greetings. I am also using some in queued signal and slot connections. See also Thread Support in Qt, QObject::connect(), qRegisterMetaType(), and Q_DECLARE_METATYPE(). The struct is declared in my worker class, which is inside a namespace. +50. 4] QString QWebSocket:: subprotocol const. in your main function or in the constructor of AudioGuiApplication. There is no way to add support for more of these value types like std::string (*). Call qRegisterMetaType() to register the data type before you establish the connection. Usually it goes in a pair: Q_DECLARE_METATYPE(TypeName) goes in the header, and then in the source at runtime registration is done with: qRegisterMetaType<TypeName>();answered May 10, 2013 at 2:25. 2）添加声明：利用宏 Q_DECLARE_METATYPE. You may have to register before you can post: click the register link above to proceed. Firstly, you shouldn't need to use Q_DECLARE_METATYPE (or qRegisterMetaType) with the enum at all, this is handled by the moc. 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. Any class or struct that has a public default constructor, a public copy constructor, and a. This replaces the now-deprecated Q_ENUMS and will automatically register the metatype. The correct syntax is Q_DECLARE_METATYPE (std::string) without the ;. // - in a header: // - define a specialization of this template calling an out-of. There's also no need for that typedef, it only makes the code less readable. There is no contradiction, because you can't register QObject descendants with Q_DECLARE_METATYPE. . 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(). Returns the internal ID used by QMetaType. Similarly you can create a mutable view of type QAssociativeIterable on any container registered with Q_DECLARE_ASSOCIATIVE_CONTAINER_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); This now makes it possible for Message values to be stored in QVariant objects and retrieved later. 4. In my project, MyClass is a cache for multi-dimensional data "point", and it looks like: class MyClass { public: MyClass(); /* Some functions */ private: int m_index; double m_time; QList<int> *m_data; };Firstly, you shouldn't need to use Q_DECLARE_METATYPE (or qRegisterMetaType) with the enum at all, this is handled by the moc. See also Thread Support in Qt, QObject::connect(), qRegisterMetaType(), and Q_DECLARE_METATYPE(). So using qRegisterMetaType () you will just trade Q_ENUM () for Q_DECLARE_METATYPE (). @Mark81 Actually you'll probably need only Q_DECLARE_METATYPE as this is done at compile time - exposing the type to the metatype system (I know it is an enum but it's needed for the QVariant and the like). Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. 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 () <<. The code compiles and runs ok. // But the split allows to. @kshegunov said: you're doing it wrong. 该类型必须有公有的 构造、析构、复制构造 函数. Some structure need to be registered to be queued in asynchronous signals using qRegisterMetaType<T>(name), such as signal which passes QVector<int>. cpp. Workaround: use a class. 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. Actually, they are declared, but in a private section with the macro Q_DISABLE_COPY(). S 1 Reply Last reply Reply Quote 0. 1. If you only want to store pointer to Foo with the metatype system, then use qRegisterMetaType<Foo *> ();. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. staticMetaObject is of type QMetaObject and provides access to the enums declared with Q_ENUMS. qRegisterMetaType<signed long long>() - do nothing. 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. 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(). Using the qRegisterMetaType () function The Q_DECLARE_METATYPE () macro is the preferred way to declare a variable in Qt. int videoSourceMetaTypeId = qRegisterMetaType< VideoSource > ();Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. Jun 13, 2021 at 19:37. Q_DECLARE_METATYPE. There's no need to call qRegisterMetaType that many times, once is enough. pro file, several errors appear referencing the QMouseEvent and QWheelEvent classes. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. 8. Learn more about Teams I can't figure out a way to automatically declare a meta type, i. The file (called a "rep" file) uses a specific (text) syntax to describe the API. qRegisterMetaType<cv::Mat>(); Modified: qRegisterMetaType< Mat >("Mat");The code generated by repc creates a Q_GADGET class for each POD, with corresponding Q_PROPERTY members for each type defined for the POD. Q_DECLARE_METATYPE, as pointed out by @SingerOfTheFall, would register template based type into QVariant (so it can be retrieved using qvariant_cast<T>()). But with the shared_ptr object, not a pointer to the shared pointer! You will have to register std::shared_ptr<yourclass> with the Qt meta object system before this can work, i. Type is not registered, please use the Q_DECLARE_METATYPE macro to make it known to Qt's meta-object system. . I want to use drag-and-drop to drag a QTreeWidgetItem that has std::shared_ptr user data.