Constantin. 如果非QMetaType内置类型要. 2、在类型定义完成后，加入声明：Q_DECLARE_METATYPE (MyDataType); 3、在main ()函数中. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. 0. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. Re: Q_DECLARE_METATYPE problem. A. 1. private: AnotherQGadgetClass test_; } Q_DECLARE_METATYPE(QGadgetClass) I am trying to access Q_GADGET from QML classic way like accessing a Q_OBJECT , but the setters are not called. Step 1 (mark for MOC), build some QObjects That pattern uses Q_PROPERTY and Q_OBJECT and the MoC tool. Don't use Q_DECLARE_METATYPE and qRegisterMetaType for your QObject enum. Make sure you call it from within a method. You can make them known ( Q_DECLARE_METATYPE ), however you can't register them as QML type. [edit] forgot to mention that you also have to use a worker object. There's no need to call qRegisterMetaType that many times, once is enough. Q_DECLARE_METATYPE(Pkg) and this does not give compile errors, but in my main. Additional types can be registered using qRegisterMetaType() or by calling registerType(). nyaruko. 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. That would allow you to use. First of all you need to declare your custom object for Qt metatype system. Call qRegisterMetaType() to make type available to non-template based functions, such as the queued signal and slot connections. When using signals and slots with multiple threads, see Signals and Slots Across Threads. Basically, I created a library containing a type: struct MyCustomType {. All Qt Overviews. 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. That always worked in Qt4, but in Qt5 I get the following error: @error: specializing member ‘::qRegisterMetaType<Subclass>’ requires ‘template<>’ syntax@. qRegisterMetaType vs. You'll need Q_DECLARE_METATYPE () if you want to store your type within a QVariant and you will additionally need qRegisterMetaType<> () if you want to dynamically create and destroy objects of that type at runtime, mostly for queued signal and slots connections or the QObject property system. When these files are processed by repc, repc generates both. hpp which is included in Class1. io Please note that I do not use Q_DECLARE_METATYPE on purpose because I don't actually need its features (QVariant expansion) right now. 12. To start viewing messages, select the forum that you want to visit from the selection below. ) summary refs log tree commit diff statsFoo and Foo* are different types and need to be registered separately. Did you also check the Q_DECLARE_METATYPE macro ?我发现qt5怎么不需要通过q_declare_metatype声明自定义的结构体，也能编译通过，使用正常啊？！！ 估计是多线程传递时，才需要使用q_declare_metatype。另外，看样子q_declare_metatype和qvariant要搭配使用。1 Answer. Share Follow edited Apr 29, 2013 at 7:21 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. qRegisterMetaType<Subclass> ("Subclass") also doesn't work. // But the split allows to. Read and abide by the Qt Code of Conduct. But I really would like to know the correct way to solve this problem; one where it is not possible to modify. Q_DECLARE_METATYPE, as pointed out by @SingerOfTheFall, would register template based type into QVariant (so it can be retrieved using qvariant_cast<T>()). Quote: bool QVariant::operator==(const QVariant & v) const. h. QtCore. For that, I want to declare a. 如果非QMetaType内置类型要. To use the type T in queued signal and slot connections,. To call qRegisterMetaType (), you still need to use Q_DECLARE_METATYPE (). To make the custom type. :) QApplication is the root QObject of the program and its full initialization is required before anything can practically be done with anything else. Share Improve this answer Follow answered Jul 23, 2014 at 15:37. rep file extension, short for Replica. your custom type definition. Type is not registered, please use the Q_DECLARE_METATYPE macro to make it known to Qt's meta-object system. typedef QVector<QSharedPointer<Tester> > TestPointerVector;. Returns the used WebSocket protocol. 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). 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。. 1. This is not the case, since the following succeeded: @QMetaType::type("MyClass"); // success@. Connect and share knowledge within a single location that is structured and easy to search. Duplicate Question(s):Q_DECLARATIVE_METATYPE in and out; Using EventExport vs. QtNetwork. If you ever wondered what does Q_DECLARE_META_TYPE or qRegisterMetaType do and when to use (or not to use) them, read on. qRegisterMetaType() docs say: Any class or struct that has a public constructor, a public copy constructor, and a public destructor can be registered. 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. If you want both, then register both. cpp 中，用connect函数 将抛出此结构体的信号和接收此结构体的槽函数关联之前，要调用qRegisterMetaType. and Q_DECLARE_METATYPE uses qRegisterMetaType() internally. 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. Current the only supported type info is QML_HAS_ATTACHED_PROPERTIES. 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. Detailed Description. Call qRegisterMetaType<std::string> (); in the initialization of your code. 1 Answer. Declare new types with Q_DECLARE_METATYPE () to make them available to QVariant and other template. I've registered my class with: @Q_DECLARE_METATYPE(MyClass);@ and. The ones I am registering for are mostly structs for storing data and just a few simple classes. 1. I have a few instances of QVector<MyClass> which I want them to be exposed to QScriptEngine. qRegisterMetaType () is called to register the TYPE and generate a TYPE ID. ", which suggests it is only for classes and structs. +50. You may have to register before you can post: click the register link above to proceed. 0. Thanks for the suggestion. 23k 10 10 gold. Since Qt 5. This version of the function is to register alias types. Franzk 26 May 2011, 06:59. The docs only talk about class or struct with public default constructor, copy constructor and. 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. Q&A for work. 2 Answers. You may have to register before you can post: click the register link above to proceed. 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. Sorted by: 2. Declare new types with Q_DECLARE_METATYPE () to make them available to QVariant and other template-based functions. Now you have a valid QObject. QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). QMetaType registerNormalizedTypedef normalizedTypeName, type: metaType ); return. @kshegunov said: you're doing it wrong. Equivalent to Q_DECLARE_METATYPE(TYPE *) and Q_DECLARE_METATYPE(QQmlListProperty<TYPE>) QML_DECLARE_TYPEINFO (Type, Flags) Declares additional properties of the given Type as described by the specified Flags. Call qRegisterMetaType() to make type available to non-template based functions, such as the queued signal and slot connections. h in the translation unit where you have that line. @Q_DECLARE_METATYPE (std::unique_ptr<Thing>);@. Is your Q_DECLARE_METATYPE in a header file or an implementation file? Incidentally, there is a mistake in TreeItem. Call qRegisterMetaType() to register the data type before you establish the connection. Specifically, the function have to be called before using the struct. 2. 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. It associates a type name to a type so that it can be created and destructed dynamically at run-time. 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. Declare new types with Q_DECLARE_METATYPE () to make them available to. Note that you are technically lying to the meta type system. I am also using some in queued signal and slot connections. 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. It seems that for a metatype that is a QList<MyClass::MyEnum> I must. 4. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. I think you need to add an explicit export/import directive to the QT_NAMESPACE macro. Q_DECLARE_METATYPE(TYPEDEF) Q_DECLARE_METATYPE(TYPEDEF) mainwindow. 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. 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. This requires the exchanged data to be of a type that is recognizable by the engine. This may make certain type comparisons fail. nyaruko. Q&A for work. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. M. QML Qvariant from custom class. 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. 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. You may have to register before you can post: click the register link above to proceed. . Even though we do not intend. 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). 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. J. This results in access violations. Declare new types with Q_DECLARE_METATYPE () to make them available. 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. Enumerations that are declared with Q_ENUM have their QMetaEnum registered in the enclosing QMetaObject. The Q_DECLARE_METATYPE() macro and qRegisterMetaType() function documentation contain more detailed information about their uses and limitations. Then you should register your object to use it with QML. Q&A for work. Yes, templated types can be used in Qt signal/slots. multithreaded software and I am getting the warning says: (Make sure 'QVector<int>' is registered using qRegisterMetaType (). qRegisterMetaType vs. // - in a header: // - define a specialization of this template calling an out-of. Qt. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. Jul 9, 2017 at 21:51. 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. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. With Q_DECLARE_METATYPE and without qRegisterMetaType: No warning, slot is called With Q_DECLARE_METATYPE and with qRegisterMetaType: No warning, slot is called. The same plugin may be loaded multiple times during the application's lifetime. Your Matrix type is not copiable, thus you can't use Q_DECLARE_METATYPE on it. As the docs state: Declare new types with Q_DECLARE_METATYPE () to make them available to QVariant and other template-based functions. complains that the metatype isn't registered. There's no need to call qRegisterMetaType that many times, once is enough. It is a static method, it does not (cannot) change x2. (Make sure 'MyStruct' is registered using qRegisterMetaType (). 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. 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. What worries me is that. Use Q_DECLARE_METATYPE (std::string) in one of your headers. 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. Make your own typedef and do the Q_DECLARE_METATYPE and qRegisterMetatype. in a header file and call @qRegisterMetaType<std::unique_ptr<Thing>> ();@ before your signal and slots are used. no I didn't, do I need to put in the file generated by repc or I can put it anywhere ? – Houss_gc. 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. 4] QString QWebSocket:: subprotocol const. I pass the MyClass pointer to the streaming operator and only stream things like QString, QPointF, etc. 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). You may have to register before you can post: click the register link above to proceed. Our first stop for registrations always is the macro Q_DECLARE_METATYPE. This function was introduced in Qt 4. As you have already found out, you must use Q_DECLARE_METATYPE to make the type known to Qt. . It associates a type name to a type so that it can be created and destructed dynamically at run-time. See also Thread Support in Qt, QObject::connect(), qRegisterMetaType(), and Q_DECLARE_METATYPE(). See the Custom Type Example for code. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. With Q_DECLARE_METATYPE and without qRegisterMetaType: No warning, slot is called With Q_DECLARE_METATYPE and with qRegisterMetaType: No warning, slot is called. J 1 Reply Last reply Reply Quote 0. 如果是指针类型他需要有完整的定义。使用Q_DECLARE_OPAQUE_POINTER()去注册指针用于转发数据类型。 使用Q_DECLARE_METATYPE()可以让这个数据类型T放到QVariant里面。如果想以队列的方式让T使用信号与槽，当第一次连接的时候就要调用qRegisterMetaType<T>()。Detailed Description. e. [override virtual] bool QLocalSocket:: waitForBytesWritten (int msecs = 30000) Reimplements:. 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. 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. So in your case you need to declare. h instead ofQVariant x2; x2. qRegisterMetaType vs. // - in a header: // - define a specialization of this template calling an out-of. Last updated at 2016-07-08 Posted at 2015-11-16. The reasoning is found in the discussion on Identity vs Value on the Qt Object Model page. [override virtual] bool QAbstractSocket:: waitForBytesWritten (int msecs = 30000) Reimplements:. Declare new types with Q_DECLARE_METATYPE () to make them available to. Greetings. 幸哉~ Qt是支持自定义信号，且自定义信号可以发送自定义数据类型的对象。. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. It associates a type name to a type so that it can be created and destructed dynamically at run-time. } 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. What worries me is that. 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. Qt Code: Switch view. To enable creation of objects at run-time, call the qRegisterMetaType() template function to register it with the meta-object system. This allows me to use this type in a Q_PROPERTY, this all. Firstly, you shouldn't need to use Q_DECLARE_METATYPE (or qRegisterMetaType) with the enum at all, this is handled by the moc. From the docs: int qRegisterMetaType ( const char * typeName ) Registers the type name typeName to the type T. said, try to directly pass shared_ptr with your signal/slots. It will return the same result if it was called before. The Q_DECLARE_METATYPE() macro and qRegisterMetaType() function documentation contain more detailed information about their uses and limitations. 步骤： (以自定义MyDataType类型为例）. This function is useful to register typedefs so they can be used by QMetaProperty, or in QueuedConnections. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. That class receives a list of variants (wrapping various data) and converts those variants into a binary stream using QDataStream >. The file (called a "rep" file) uses a specific (text) syntax to describe the API. I only care about runtime instantiation. QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_REGISTER_METATYPE() and qRegisterMetaType(). From the QVariant::value documentation: If the QVariant contains a pointer to a type derived from QObject then T may be any QObject type. 1 Answer. Remember that Q_DECLARE_METATYPE merely defines a specialization of QMetaTypeId for your type. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. ompiler (repc) generates header files based on an API definition file. 基本理解. I meet a qt metatype issue. This replaces the now-deprecated Q_ENUMS and will automatically register the metatype. Yes I tried with qRegisterMetaType, it. 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. @Daddedebad As @Bonnie says qRegisterMetaType. void QAbstractSocket:: abort ()2 Answers. 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. ) 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. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. container. The QML engine provides built-in support for a. pro file, several errors appear referencing the QMouseEvent and QWheelEvent classes. There's no need to call qRegisterMetaType that many times, once is enough. Tried proposed solution using QVariant::fromValue, but kept getting compiler errors of type: . Now, that Q_DECLARE_METATYPE enables the type for Qt template classes and QVariant. Also Q_DECLARE_METATYPE does not register a type, but declares it. Any class or struct that has a public constructor, a public copy constructor, and a public destructor can be registered. I tried to write one, but I failed. I think you need to add an explicit export/import directive to the QT_NAMESPACE macro. To register. 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. 2. Q_DECLARE_METATYPE. Re: How to use Q_DECLARE_METATYPE. One of these plugins uses Q_DECLARE_METATYPE on some types that need to be stored in a QVariant. Type is not registered, please use the Q_DECLARE_METATYPE macro to make it known to Qt's meta-object system. For pointer types, it also requires that the pointed to type is fully defined. 14 vs 5. Detailed Description. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. x however, the code generated by moc will call qRegisterMetaType for you if moc can determine that the type may be registered as a meta-type. 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. There's also no need for that typedef, it only makes the code less readable. Q_GADGET makes a class member, staticMetaObject, available. Any class or struct that has a public default constructor, a public copy constructor, and a. 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. Does your code ever call qRegisterMetatype() or use Q_DECLARE_METATYPE()? 10th November 2014, 06:23 #3. Here you can see that the macro expands to nothing. As a workaround, I'm using QVariantMap instead of std::map. I thought there was a bug with QMetaType or Q_DECLARE_METATYPE. To start viewing messages, select the forum that you want to visit from the selection below. Share. @kshegunov said in Undocumented automatic metatype registration in Qt6?: Your original code (in the top-mentioned topic) assumes std::unique_ptr is copyable, which it isn't, so it can not ever be a metatype. call qRegisterMetaType with the name specified, else reading properties. Has anyone else encountered this?See also qRegisterMetaType(). QMetaType::type () is a bit slower, but compilation succeeds if a type is not registered. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. 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. Normally, you would only register the pointer form if your class cannot be copied, as in the case of QObject and derivatives, but. ) 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. Any class or struct that has a public default constructor, a public copy. rep file extension, short for Replica. More. e. Jun 13, 2021 at 19:37. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. Registered enumerations are automatically registered also to the Qt meta type system, making them known to QMetaType without the need to use Q_DECLARE_METATYPE(). EDIT: When you convert your class to QVariant it uses a. . You should use qmlRegisterType function for that. Then the TYPE ID is saved in local static vairable metatype_id. So my first idea:. As said in int qRegisterMetaType () documentation: To use the type T in QVariant, using Q_DECLARE_METATYPE () is sufficient. 8. I read on documentation that Q_DECLARE_METATYPE makes available type to QVariant, for example (I got it from documentation): @ struct MyStruct { int i;. One of these plugins uses Q_DECLARE_METATYPE on some types that need to be stored in a QVariant. I am also using some in queued signal and slot connections. Q_DECLARE_METATYPE accepts objects with public constructor, copy constructor and destructor. no unexpected garbage. So my first idea:. 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. 12. So I am doing this: Qt Code: Switch view. Jun 13, 2021 at 19:37. 3 to Qt4. QLocalSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). 4] QString QWebSocket:: subprotocol const. 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. 8. If you want both, then register both. waitForConnected ([msecs=30000]) # Parameters: msecs – int. qRegisterMetaType<signed long long>() - do nothing. The QMetaType class manages named types in the meta-object system. Improve this answer. @Q_DECLARE_METATYPE (std::unique_ptr<Thing>);@. 0. Q_OBJECT derived class, inheritance. To start viewing messages, select the forum that you want to visit from the selection below. S 1 Reply Last reply Reply Quote 0. The fix is probably to include qsslsocket. Q_DECLARE_METATYPE(TYPEDEF) Q_DECLARE_METATYPE(TYPEDEF) mainwindow. You could also Q_DECLARE_METATYPE to register your custom type and then use qMetaTypeId() to get the metaType id. 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. 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. "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. 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. . See also Thread Support in Qt, QObject::connect(), qRegisterMetaType(), and Q_DECLARE_METATYPE(). It does not say anything about registering the type. Also Q_DECLARE_METATYPE does not register a type, but declares it. 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. In the header, after the class declaration, outside the namespace, I've included. e. Execute qRegisterMetaType<QItemSelection> (); before it is used as such, e. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. @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). 1. fromValue <QList<double> > ( x1); To copy to clipboard, switch view to plain text mode. I want to use drag-and-drop to drag a QTreeWidgetItem that has std::shared_ptr user data. I guess it's the qRegisterMetaType () call itself that's missing. Re: Qt warning of type conversion already registered Originally. 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. 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. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. I am also using some in queued signal and slot connections. QVariant x2 = QVariant::fromValue( x1); To copy to clipboard, switch view to plain text mode. To use the type T in queued signal and slot connections, qRegisterMetaType<T>() must be called before the first connection is established. 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(). So in your case you need to declare. since it is a runtime registration. See also state() and Creating Custom Qt Types. QVariantList MyClass::getFooCollection (void) const { QVariantList list; for (const auto& l: fooCollection_) { list. 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. 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. This also makes the type available for queued. in a header file and call @qRegisterMetaType<std::unique_ptr<Thing>> ();@ before your signal and slots are used.