I simplified the code quite a bit and the problem went away. Any class or struct that has a public constructor, a public copy constructor, and a public destructor can be registered. ", which suggests it is only for classes and structs. We all have started by asking questions. state() Creating Custom Qt Types. To start viewing messages, select the forum that you want to visit from the selection below. There's no need to call qRegisterMetaType that many times, once is enough. 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. 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. It manages an insane amount of static variables and sets a static global pointer of. qRegisterMetaType vs. call qRegisterMetaType() to register the data type before you establish the connection. By convention, these files are given a . To achieve this you need Q_DECLARE_METATYPE macro and qRegisterMetaType () function. 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。. To start viewing messages, select the forum that you want to visit from the selection below. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. . After googling this, I found this correspondence, which was only available through a third party archival site as google. The correct syntax is Q_DECLARE_METATYPE (std::string) without the ;. 12. If you are using queued connections, you need to register std::string as meta type. That's created by this macro. To start viewing messages, select the forum that you want to visit from the selection below. I pass the MyClass pointer to the streaming operator and only stream things like QString, QPointF, etc. If you want both, then register both. That. 2. All I want to do is be able to convert this to a byte array in order to send on a socket, and get the object back (deserialize) on the other end. 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(). J 1 Reply Last reply Reply Quote 0. This macro is used to specialise the template class QMetaTypeId with typename TYPE, in which, a static member function qt_metatype_id () is defined. There's also no need for that typedef, it only makes the code less readable. complains that the metatype isn't registered. The Custom Type and Queued Custom Type examples show how to implement a custom type with the features outlined in this document. (Make sure 'MyStruct' is registered using qRegisterMetaType (). 16. 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. 4 which does not support all C++11 features. To register VideoMeta you need to call qRegisterMetaType<VideoMeta>(). Learn more about Teams Declaring a meta type. 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. QObject can't be copied and all its descendants can't be copied also. 2. qRegisterMetaType vs. For that, I want to declare a. As said in int qRegisterMetaType () documentation: To use the type T in QVariant, using Q_DECLARE_METATYPE () is sufficient. Assuming base and derived are Q_GADGETs you want to get a static member. I believe this is related to the fact that. This example is meant to declare and register only the pointer type of a given class: In conclusion: Don't use Q_DECLARE_METATYPE and qRegisterMetaType for your QObject enum. type() typeName() PySide6. It associates a type name to a type so that it can be created and destructed dynamically at run-time. Note: This function is thread-safe. Qt has to stay free or it will die. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. 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. To use the type T in QVariant, using Q_DECLARE_METATYPE() is sufficient. When these files are processed by repc, repc generates both. See also Thread Support in Qt, QObject::connect(), qRegisterMetaType(), and Q_DECLARE_METATYPE(). You should use Q_DECLARE_METATYPE macro for this. Make sure you call it from within a method. You don't pass around copies of QObject derived types because it is not copyable. I have declared all the types with Q_DECLARE_METATYPE, Q_OBJECT and the properties with Q_PROPERTY with the proper getters and setters. Duplicate Question(s):Q_DECLARATIVE_METATYPE in and out; Using EventExport vs. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. Declare new types with Q_DECLARE_METATYPE () to make them available. The Rep lica C ompiler (repc) generates QObject header files based on an API definition file. QVariant’s operator== now uses QMetaType::equals for the comparison. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. The "traditional" way of doing this is to convert each element to a QVariant, and pass collection as a QVariantList. ) I have defined MyStruct in an accessible header file: myheader. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. in your main function or in the constructor of AudioGuiApplication. QVariant x2 = QVariant::fromValue( x1); To copy to clipboard, switch view to plain text mode. Q_DECLARE_METATYPE () doesn't actually register the type; you must still use qRegisterMetaType () for that, particularly if you intend to use the type in signal and slot connections. 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). See also state(). qRegisterMetaType() docs say: Any class or struct that has a public constructor, a public copy constructor, and a public destructor can be registered. Detailed Description The QMetaType class manages named types in the meta-object system. The macro will register your variable with the Qt Meta-Object System, which will allow you to. . QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). Yes, templated types can be used in Qt signal/slots. Qt Base (Core, Gui, Widgets, Network,. enum Qt:: ContextMenuPolicycall qRegisterMetaType() to register the data type before you call QMetaMethod::invoke(). See also state () and Creating Custom Qt Types . statement to the header file containing. Note that for enum types, you no not even need to call qRegisterMetaType () in these cases. 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. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. Obviously then you would not do registerComparator (). So I tried declaring the following at end of my worker thread class Q_DECLARE_METATYPE(cv::Mat);. See also. Using Q_ENUM () allows you to retrieve at run-time. Make a typedef for QSharedPointer<UserDataType>, and use both Q_DECLARE_METATYPE as well as qRegisterMetaType () to register it for use. 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. I placed Q_DECLARE_METATYPE (DataPoint) after the class definition. 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. // - in a header: // - define a specialization of this template calling an out-of. By convention, these files are given a . The default access for a class is private, so that Container* data();. I my real world application Context holds a large number of physical quantities (masses, forces, velocities,. Also Q_DECLARE_METATYPE does not register a type, but declares it. 14. 1. 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. To start viewing messages, select the forum that you want to visit from the selection below. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. 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. until today. This also makes the type available for queued. You may have to register before you can post: click the register link above to proceed. 11. 4 which does not support all C++11 features. 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. Q_DECLARE_METATYPE accepts objects with public constructor, copy constructor and destructor. Constantin. The class is used as a helper to marshall types in QVariant and in queued. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries that are used. Declare new types with Q_DECLARE_METATYPE () to make them available to. Q_DECLARE_METATYPE(TYPEDEF) Q_DECLARE_METATYPE(TYPEDEF) mainwindow. Good workaround: you may register your type with Q_DECLARE_METATYPE ( IBase * ) macro and wrap your variable. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. Assuming base and derived are Q_GADGETs you want to get a static member. The struct is declared in my worker class, which is inside a namespace. If you have to use Q_DECLARE_METATYPE yourself, the id is not constexpr. Since \c{MyStruct} is now known to QMetaType, it can be used in QVariant: Some types are registered automatically and do not need this macro: /*! This macro makes the container \a Container known to QMetaType as a sequential. It will return the same result if it was called before. 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. You could try using registerConverter () to allow implicit conversion of the shared_ptr<int> to a regular int, and compare them that way. If the type was not declared with Q_DECLARE_METATYPE (), compilation will fail. Also, to use type T with the QObject::property () API, qRegisterMetaType () must be. 24th July 2010, 09:54 #6. :) QApplication is the root QObject of the program and its full initialization is required before anything can practically be done with anything else. 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. This is not the case, since the following succeeded: @QMetaType::type("MyClass"); // success@. void QAbstractSocket:: abort ()Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. 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. 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. Any class or struct that has a public constructor, a public copy constructor, and a public destructor can be registered. 0. Believing an Question from 2010 and the Qt Documentation, the operator==() doesn't work with custom types. {. g. 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. The other overload around has almost the same form but for the. 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. 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. @Q_DECLARE_METATYPE (std::unique_ptr<Thing>);@. 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. e. Declare new types with Q_DECLARE_METATYPE () to make them available to QVariant and other template-based functions. 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. Using the macro directly turned out to be impossible. canConvert<x> (); } and. Q_DECLARE_METATYPE(MyStruct) Q_DECLARE_METATYPE(MyList) QDBusArgument &operator<<(QDBusArgument &, const MyStruct&);. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. Obviously, a call to qRegisterMetaType<T>(. To start viewing messages, select the forum that you want to visit from the selection below. Then you should register your object to use it with QML. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. 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. 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. I tried to write one, but I failed. Good workaround: you may register your type with Q_DECLARE_METATYPE ( IBase * ) macro and wrap your. This fixed the issue. +50. See also Thread Support in Qt, QObject::connect(), qRegisterMetaType(), and Q_DECLARE_METATYPE(). Note that you are technically lying to the meta type system. Q_DECLARE_METATYPE(TYPEDEF) Q_DECLARE_METATYPE(TYPEDEF) mainwindow. 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. e. Connect and share knowledge within a single location that is structured and easy to search. } 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. Obviously then you would not do registerComparator (). The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. So, whatever Q_DECLARE_METATYPE is doing cannot be done by writing a function call. See also state() and Creating Custom Qt Types. I'm confused by this error, as the documentation states (emphasis mine): Returns the meta type id of type T at compile time. This allows me to use this type in a Q_PROPERTY, this all. 23k 10 10 gold. See the Custom Type Example for code. 4] QString QWebSocket:: subprotocol const. The fix is probably to include qsslsocket. I just tried. Declare new types with Q_DECLARE_METATYPE () to make them available. In the header, after the class declaration, outside the namespace, I've included. 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. 0. 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. View Profile View Forum Posts View Articles Beginner Join Date Nov 2014 Posts 6 Qt products. Read and abide by the Qt Code of Conduct. The file (called a "rep" file) uses a specific (text) syntax to describe the API. I also added qRegisterMetaType<DataPoint> () to the initialisation method of my main. 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. Call qRegisterMetaType() to register the data type before you establish the connection. Now you have a valid QObject. void QLocalSocket:: abort ()The signal "orientationChanged" includes an enum of type "Orientation" to indicate if the card has been turned up or down. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. See also. 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. This function was introduced in Qt 4. With Q_DECLARE_METATYPE and without qRegisterMetaType: No warning, slot is called With Q_DECLARE_METATYPE and with qRegisterMetaType: No warning, slot is called. container. 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. Compares this QVariant with v and returns true if they are equal;. It does not say anything about registering the type. With Q_DECLARE_METATYPE and without qRegisterMetaType: No warning, slot is called With Q_DECLARE_METATYPE and with qRegisterMetaType: No warning, slot is called. @kshegunov said: you're doing it wrong. In the example's Message class, a static method is included to do this. See also state() and Creating Custom Qt Types. QtCore. nyaruko. goocreations 12 Mar 2013, 07:22. Per Qt documentation: To use the type T in QVariant, using Q_DECLARE_METATYPE () is sufficient. You are looking for the Q_ENUM () macro. Q_DECLARE_METATYPE on the other hand is (as far as I know) preprocessor bound. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. This function was introduced in Qt 6. Q_DECLARE_METATYPE only registers a type in meta type system. You can also use QMetaEnum::fromType() to get the QMetaEnum. 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. 2）添加声明：利用宏 Q_DECLARE_METATYPE. Re: Qt warning of type conversion already registered Originally. qRegisterMetaType<Subclass> ("Subclass") also doesn't work. @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. The Q_DECLARE_METATYPE() macro and qRegisterMetaType() function documentation contain more detailed information about their uses and limitations. So in your case you need to declare. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. 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. I have added Q_DECLARE_METATYPE(quint32) in Class2. The Q_DECLARE_METATYPE() macro and qRegisterMetaType() function documentation contain more detailed information about their uses and limitations. From the docs: int qRegisterMetaType ( const char * typeName ) Registers the type name typeName to the type T. In. 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. QtCore. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. 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. That's probably there, as qRegisterMetaType () wouldn't compile otherwise. ) QObject::connect: Cannot queue arguments of type 'QVector<int>'. Call qRegisterMetaType() to make type available to non-template based functions, such as the queued signal and slot connections. Q_DECLARE_METATYPE QMetaType::type. 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. QMetaType registerNormalizedTypedef normalizedTypeName, type: metaType ); return. 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. Also, to use type T with the QObject::property () API,. You may have to register before you can post: click the register link above to proceed. [override virtual] bool QAbstractSocket:: waitForBytesWritten (int msecs = 30000) Reimplements: QIODevice::waitForBytesWritten(int. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. 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. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries that are used. The Q_DECLARE_METATYPE() macro and qRegisterMetaType() function documentation contain more detailed information about their uses and limitations. First of all you need to declare your custom object for Qt metatype system. 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. h" class B : public QObject { Q_OBJECT Q_PROPERTY(A* A1 READ getA1 WRITE setA1) Q_PROPERTY(A* A2 READ getA2 WRITE setA2) public: static A A1;. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. See the Qt D-Bus Type System page for more information on the type system. 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. I want to use my objects as QVariants and for queued connections. I want to use drag-and-drop to drag a QTreeWidgetItem that has std::shared_ptr user data. M. Re: How to use Q_DECLARE_METATYPE. Call qRegisterMetaType () to make type available to non-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. I have an application that requires use of both Qt 3D and the QCustomPlot library. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. [override virtual] bool QAbstractSocket:: waitForBytesWritten (int msecs = 30000) Reimplements:. in a header file and call @qRegisterMetaType<std::unique_ptr<Thing>> ();@ before your signal and slots are used. You can register a class pointer as the metatype, though. I read a bit and it seems that Q_DECLARE_SMART_POINTER_METATYPE is supposed to allow this to work. int videoSourceMetaTypeId = qRegisterMetaType< VideoSource > ();QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). This replaces the now-deprecated Q_ENUMS and will automatically register the metatype. 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. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. QList of Custom Objects. You can also use QMetaEnum::fromType() to get the QMetaEnum. But I can't see a method to insert myClass into. To start viewing messages, select the forum that you want to visit from the selection below. I also don't want to use qRegisterMetaType, since it is run-time bound. QLocalSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). QtCore. QLocalSocket. 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. h) of the derived class. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. In Qt, you can declare a variable in two ways: 1. Q_DECLARE_METATYPE(MyClass); qRegisterMetaType<MyClass>(); I can use the type in queued connection with signals like this one: void MySignal(MyType o); Now I also would like to use the type with signals like this: void MyVectorSignal(QVector<MyType> v);Qt 5. See also state() and Creating Custom Qt Types. It must appear in a code block. 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. on top of main. . cpp. qRegisterMetaType vs. due to requirements at my job, I had to revert by build from Qt5. The object it returns should also be a member of the factory class. Q&A for work. 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. G. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. The reasoning is found in the discussion on Identity vs Value on the Qt Object Model page. (Make sure 'QVector<int>' is. 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. In some cases in Qt 4, it is also necessary to use the qRegisterMetaType method. Also, Q_DECLARE_METATYPE(MyNamespace::MyType) should be in the header declaring MyType so that you don't have to repeat it all over again and again. But there would be no trouble using the QMetaType class or using qRegisterMetaType before creating an instance of QCoreApplication or QApplication. qRegisterMetaType vs. Normally, you would only register the pointer form if your class cannot be copied, as in the case of QObject and derivatives, but. Q_DECLARE_METATYPE ( blabla* ) Also qRegisterMetaType<T> () is only required for sending your object through queued signal/slot connections. [virtual] QLocalSocket:: ~QLocalSocket Destroys the socket, closing the connection if necessary. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. You can use Q_DECLARE_METATYPE(Widget*) but it is not needed as of Qt. Any idea what I'm missing please? BTW, no problem at all using Schedule in QMetaProperty or QVariant. Basically, I created a library containing a type: struct MyCustomType {. I think you need to add an explicit export/import directive to the QT_NAMESPACE macro. So you can call it from your constructor. Q_DECLARE_METATYPE(shared_ptr<SomeClass> const &) qRegisterMetaType<shared_ptr<SomeClass> const&>(); 许多标准API都有 QString const & ，因此我认为从根本上来说是可能的，而我只是想不出语法。You actually need to do it once (i. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. Accessing an enum stored in a QVariant. e. Now, that Q_DECLARE_METATYPE enables the type for Qt template classes and QVariant. I have a problem with a class that exchanges data using TCP/IP socket. Note: it's also safe to call qRegisterMetaType () multiple times. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. There's no compile time error, but when I run. After googling this, I found this correspondence, which was only available through a third party archival site as google. 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 (. Is your Q_DECLARE_METATYPE in a header file or an implementation file? Incidentally, there is a mistake in TreeItem. Q_DECLARE_METATYPE. enum Qt:: ContextMenuPolicyQObject has neither a copy constructor nor an assignment operator. genC last edited by . struct StandardData { int EmpId; QString Name; }; Q_DECLARE_METATYPE (StandardData) Additionally, you might need to call qRegisterMetaType. QML_DECLARE_TYPE. Tried proposed solution using QVariant::fromValue, but kept getting compiler errors of type: . Once they're known you can use them, but you can't create them on the QML side. Email This BlogThis! Share to Twitter Share to Facebook Share to Pinterest. First of all you need to declare your custom object for Qt metatype system. For this, a function call (evaluated during runtime) needs to be made, and qRegisterMetatype is the tool for this: qRegisterMetaType<Area>("Area");@julio. [virtual] QLocalSocket:: ~QLocalSocket Destroys the socket, closing the connection if necessary. When using signals and slots with multiple threads, see Signals and Slots Across Threads. e. To start viewing messages, select the forum that you want to visit from the selection below. Remember that Q_DECLARE_METATYPE merely defines a specialization of QMetaTypeId for your type. 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. I am also using some in queued signal and slot connections. 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. 该类型必须有公有的 构造、析构、复制构造 函数. If the type was not declared with Q_DECLARE_METATYPE (), compilation will fail. There's no need to call qRegisterMetaType that many times, once is enough. All Qt Overviews. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. The QML engine provides built-in support for a. 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 () << v. The Custom Type, Custom Type Sending and Queued Custom Type examples show how to implement a custom type with the features outlined in this document. It associates a type name to a type so that it can be created and destructed dynamically at run-time. 9k 9 34 52. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. 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. As you have already found out, you must use Q_DECLARE_METATYPE to make the type known to Qt. To start viewing messages, select the forum that you want to visit from the selection below. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. Situation. Q_DECLARE_METATYPE. Q_DECLARE_METATYPE(Pkg) and this does not give compile errors, but in my main. Quote: bool QVariant::operator==(const QVariant & v) const. I read a bit and it seems that Q_DECLARE_SMART_POINTER_METATYPE is supposed to allow this to work. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. You can make them known ( Q_DECLARE_METATYPE ), however you can't register them as QML type. 1. 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. I only care about runtime instantiation. Execute qRegisterMetaType<QItemSelection> (); before it is used as such, e. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. 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 a header: // - define a specialization of this template calling an out-of. call qRegisterMetaType with the name specified, else reading properties. From the QVariant::value documentation: If the QVariant contains a pointer to a type derived from QObject then T may be any QObject type. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. To enable creation of objects at run-time, call the qRegisterMetaType() template function to register it with the meta-object system. 5 is compiled with GCC 4. qRegisterMetaType you'll need if creating objects by class name dynamically, and it seems for queued connections,. 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. Q_DECLARE_METATYPE only registers a type in meta type system. Returns the internal ID used by QMetaType. 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. Adding a Q_DECLARE_METATYPE () makes the type known to all template based functions, including QVariant. Thanks for the suggestion. Q_DECLARE_METATYPE(MyClass*); That's how Qt handles it with QObject and QWidget. 2. Q_DECLARE_METATYPE (T) requires the type T to be default-constructable, copiable and destructable. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. 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. Q_DECLARE_METATYPE vs qRegisterMetaType for non global namespace classes. 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 no need to call qRegisterMetaType that many times, once is enough. In that case, I think you need to register them.