// - in a header: // - define a specialization of this template calling an out-of. QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). Step 1 (mark for MOC), build some QObjects That pattern uses Q_PROPERTY and Q_OBJECT and the MoC tool. 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。. When using signals and slots with multiple threads, see Signals and Slots Across Threads. Q_DECLARE_METATYPE only registers a type in meta type system. First of all, you always need to declare your meta type: Q_DECLARE_METATYPE (foo::MyClass) It works at compile time, so there are no limitations on how you refer to your class. qRegisterMetaType vs. You could also Q_DECLARE_METATYPE to register your custom type and then use qMetaTypeId() to get the metaType id. However, when attempting to compile QCustomPlot in a project using "QT += 3dinput" in its . M. Because Foo is not derived from QObject and QVariant only supports polymorphism for QObject -derived types. qt. It does not say anything about registering the type. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. I have a problem with a class that exchanges data using TCP/IP socket. This function returns the Qt meta type id for the type (the same value that is returned from qRegisterMetaType()). There's no need to call qRegisterMetaType that many times, once is enough. 基本理解. This may make certain type comparisons fail. If the type was not declared with Q_DECLARE_METATYPE (), compilation will fail. 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 to QVariant and other template-based functions. In short, I get following error: QObject::connect: Cannot queue arguments of type 'cv::Mat' (Make sure 'cv::Mat' is registered using qRegisterMetaType (). If you have to use Q_DECLARE_METATYPE yourself, the id is not constexpr. The other overload around has almost the same form but for the fact that it. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. 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. Re: How to use Q_DECLARE_METATYPE. If you ever wondered what does Q_DECLARE_META_TYPE or qRegisterMetaType do and when to use (or not to use) them, read on. To start viewing messages, select the forum that you want to visit from the selection below. no I didn't, do I need to put in the file generated by repc or I can put it anywhere ? – Houss_gc. [override virtual] bool QLocalSocket:: waitForBytesWritten (int msecs = 30000) Reimplements:. cruz Hello, To be completely candid, I haven't used GDB remotely and I'm certainly not so intimate with it for the log to speak to me much. By the way, Qt 4. For pointer types, it also requires that the pointed to type is fully defined. For those who follow. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. This is by design. QVariant v = QVariant::fromValue<cMyClass>(MyObject); However, as soon as I use Q_DECLARE_METATYPE, I get errors about using a deleted function. Greetings. In some cases in Qt 4, it is also necessary to use the qRegisterMetaType method. 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. It associates a type name to a type so that it can be created and destructed dynamically at run-time. cpp. G. As the docs state: Declare new types with Q_DECLARE_METATYPE () to make them available to QVariant and other template-based functions. It does not say anything about registering the type. It's a bit convoluted to follow, and definitely depends on which Qt modules have been included (the meta type system is designed to be expandable this way -- eg. QLocalSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). ompiler (repc) generates header files based on an API definition file. }; Q_DECLARE_METATYPE (MyCustomType); Then in my application, I have a signal "void sendMsg (MyCustomType)" and I qRegisterMetaType (). Using the following required me to use Q_DECLARE_METATYPE. There's also no need for that typedef, it only makes the code less readable. But I really would like to know the correct way to solve this problem; one where it is not possible to modify. Step 1 (mark for MOC), build some QObjects That pattern uses Q_PROPERTY and Q_OBJECT and the MoC tool. qRegisterMetaType vs. nyaruko. First of all you need to declare your custom object for Qt metatype system. Registers the type name . But I really would like to know the correct way to solve this problem; one where it is not possible to modify the template classes. Re: Q_DECLARE_METATYPE problem. So I don't stream the pointer itself just copy the properties and set them to a new created pointer object. hi, I always after application running, receive debug text of: QObject::connect: Cannot queue arguments of type 'MyStruct'. Read and abide by the Qt Code of Conduct. 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. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries that are used. You may have to register before you can post: click the register link above to proceed. This version of the function is to register alias types. Using the Q_DECLARE_METATYPE () macro 2. Improve this answer. 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 object it returns should also be a member of the factory class. And once all of them are updated I'd like the Context object to inform QML to update the view. 1 Answer. (Make sure 'QVector<int>' is. Q_DECLARE_METATYPE. I'm confused by this error, as the documentation states (emphasis mine): Returns the meta type id of type T at compile time. Q_DECLARE_METATYPE on the other hand is (as far as I know) preprocessor bound. The QMetaType class manages named types in the meta-object system. Q_DECLARE_METATYPE(MyObject*) somewhere in your code. 0. See also state(). There's no such thing as a "const reference" because references are always const -- you can't reseat them. I think you need to add an explicit export/import directive to the QT_NAMESPACE macro. 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. 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. Declare new types with Q_DECLARE_METATYPE () to make them available to QVariant and other template. As you have already found out, you must use Q_DECLARE_METATYPE to make the type known to Qt. This macro is used to specialise the template class QMetaTypeId with typename TYPE, in which, a static member function qt_metatype_id () is defined. QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_REGISTER_METATYPE() and qRegisterMetaType(). 2 Answers. qRegisterMetaType vs. As said in int qRegisterMetaType () documentation: To use the type T in QVariant, using Q_DECLARE_METATYPE () is sufficient. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. type() typeName() PySide6. Qt. This results in access violations when Qt. The following should work: Note that you also have to call qRegisterMetaType<MyMpiMessage> (); before you use the function the first time. It is often easier and cleaner to define an ENUM inside a class (see ENUM), but if you need a standalone enum type, using the ENUM keyword outside of a class definition can be. Of course it's a bug and an odd mistake that Q_DECLARE_METATYPE(QList<QSslError>) is in qsslsocket. no unexpected garbage. By convention, these files are given a . Similarly you can create a mutable view of type QAssociativeIterable on any container registered with Q_DECLARE_ASSOCIATIVE_CONTAINER_METATYPE(). See the Custom Type Example for code. Output:Additionally Q_DECLARE_METATYPE and qRegisterMetaType are not purposed to be used for QObject derived classes. jsulm Lifetime Qt Champion @shivaVMC last edited by . 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. Type is not registered, please use the Q_DECLARE_METATYPE macro to make it known to Qt's meta-object system. Any errors from Qt's metatype systems are usually due to MOC (the "meta-object compiler"), which reads your header files and generates a "moc" file with metatype information for every class where the Q_OBJECT macro is declared. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. goocreations 12 Mar 2013, 07:22. // This primary template calls the -Implementation, like all other specialisations should. To call qRegisterMetaType (), you still need to use Q_DECLARE_METATYPE (). 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. From the docs: int qRegisterMetaType ( const char * typeName ) Registers the type name typeName to the type T. 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. 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. See also state () and Creating Custom Qt Types . QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). @Daddedebad As @Bonnie says qRegisterMetaType. In that case, I think you need to register them. QML Qvariant from custom class. Re: How to use Q_DECLARE_METATYPE. This worked very well. Did you also check the Q_DECLARE_METATYPE macro ? You should declare and register the types properly, lying to qRegisterMetaType will get you in trouble in the long run. 4. your custom type definition. Even though we do not intend. Q_DECLARE_METATYPE(Pkg) and this does not give compile errors, but in my main. Here you can see that the macro expands to nothing. There's no compile time error, but when I run. I meet a qt metatype issue. View Profile View Forum Posts View Articles Beginner Join Date Nov 2014 Posts 6 Qt products. Registered enumerations are automatically registered also to the Qt meta type system, making them known to QMetaType without the need to use. SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). Call qRegisterMetaType() to make type available to non-template based functions, such as the queued signal and slot connections. Add qRegisterMetaType and qDBusRegisterMetaType calls to enable the framework to work with the custom type. The QMetaType class manages named types in the meta-object system. Also you may need to use qRegisterMetaType function. append (QVariant::fromValue (l)); } return list; } The metatype system declaration and registration you have. Re: Qt warning of type conversion already registered Originally. 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. Obviously, a call to qRegisterMetaType<T>(. Your code should look like this: Q_ENUM (StateEnum) //note the missing 'S' here Q_PROPERTY (StateEnum state READ state NOTIFY stateChanged) Share. See also disconnect(), sender(), qRegisterMetaType(), Q_DECLARE_METATYPE(), and Differences between String-Based and. Declare new types with Q_DECLARE_METATYPE () to make them available. Note that for enum types, you no not even need to call qRegisterMetaType () in these cases. Gerald Gerald. 8. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. 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. Q_DECLARE_METATYPE, as pointed out by @SingerOfTheFall, would register template based type into QVariant (so it can be retrieved using qvariant_cast<T>()). 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. h. 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. Use Q_DECLARE_OPAQUE_POINTER () to be able to register pointers to forward. As said in int qRegisterMetaType () documentation: To use the type T in QVariant, using Q_DECLARE_METATYPE () is sufficient. To use the type T in queued signal and slot connections, qRegisterMetaType () must be called before the first connection is established. But at run time, I got below error:1 Answer. queued connections. ) which are updated by simulation code. so that was all, but remember to use Q_DECLARE_METATYPE, qRegisterMetaType macros for registering your custom type with Qt meta object system. Accessing an enum stored in a QVariant. See also state() and Creating Custom Qt Types. Connect and share knowledge within a single location that is structured and easy to search. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. h) of the derived class. 0. To start viewing messages, select the forum that you want to visit from the selection below. The class is used as a helper to marshall types in QVariant and in queued. How: I linked qRegisterMetaType. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. Q_DECLARE_METATYPE(TYPEDEF) Q_DECLARE_METATYPE(TYPEDEF) mainwindow. e. When the plugin is reloaded later, the old declaration still points to the original memory space of the now-unloaded library. So I am doing this: Qt Code: Switch view. This results in access violations. 23k 10 10 gold. It associates a type name to a type so that it can be created and destructed dynamically at run-time. This allows me to use this type in a Q_PROPERTY, this all. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. What is(are) the good place(s) to put the qRegisterMetaType call? I obviously don't want any expllicit initialization. It is not safe to make a QObject's copy constructor public. When these files are processed by repc, repc generates both. I have created an qt bugticket hoping the documentation will be extended. Q_DECLARE_META_TYPE (Fruit) and qRegisterMetaType were redundant: #define PluginInterface_iid "pluginInterface" Q_DECLARE_INTERFACE (PluginInterface, PluginInterface_iid) //Actual plugin implementing PluginInterface class. Make sure you call it from within a method. Please note that I do not use Q_DECLARE_METATYPE on purpose because I don't actually need its features (QVariant expansion) right now. Any class or struct that has a public default constructor, a public copy. As the docs state: Declare new types with Q_DECLARE_METATYPE () to make them available to QVariant and other template-based functions. Declare new types with Q_DECLARE_METATYPE () to make them available to. Since Qt 5. I placed Q_DECLARE_METATYPE (DataPoint) after the class definition. Read and abide by the Qt Code of Conduct. After googling this, I found this correspondence, which was only available through a third party archival site as google. 7. the type name must be specified without the class, as in. To make the custom. See also state() and Creating Custom Qt Types. g. Enum has been moved from outside of the class to inside of it. Remember that Q_DECLARE_METATYPE merely defines a specialization of QMetaTypeId for your type. Qt has to stay free or it will die. Any class or struct that has a public constructor, a public copy constructor, and a public destructor can be registered. 4 which does not support all C++11 features. Assuming base and derived are Q_GADGETs you want to get a static member. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. The Q_DECLARE_METATYPE() macro and qRegisterMetaType() function documentation contain more detailed information about their uses and limitations. Qt Base (Core, Gui, Widgets, Network,. Call qRegisterMetaType() to register the data type before you establish the connection. Enumerations that are declared with Q_ENUM have their QMetaEnum registered in the enclosing QMetaObject. Learn more about Teams Declaring a meta type. See also. . in a header file and call @qRegisterMetaType<std::unique_ptr<Thing>> ();@ before your signal and slots are used. You may have to register before you can post: click the register link above to proceed. Detailed Description The QMetaType class manages named types in the meta-object system. This now makes it possible for Message values to be stored in QVariant objects and retrieved later. 6. Is your feature request related to a problem? No, it's an improvement Please describe. fromValue <QList<double> > ( x1); To copy to clipboard, switch view to plain text mode. 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. Although I'm. Q_DECLARE_METATYPE. qRegisterMetaType you'll need if creating objects by class name dynamically, and it seems for queued connections,. EDIT: When you convert your class to QVariant it uses a. It looks like one can register a type more than once, specifying different typenames, i. QtCore. Any class or struct that has a public default constructor, a public copy. QLocalSocket. 11. I thought there was a bug with QMetaType or Q_DECLARE_METATYPE. 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 same plugin may be loaded multiple times during the application's lifetime. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. To copy to clipboard, switch view to plain text mode. The same plugin may be loaded multiple times during the application's lifetime. ) I got the hint "expected a declaration" when I tried to use qRegisterMetaType from the global scope in my cpp file. akshatrai91 7 Jan 2021, 06:21. Share. Some structure need to be registered to be queued in asynchronous signals using qRegisterMetaType<T>(name), such as signal which passes QVector<int>. Call qRegisterMetaType<std::string> (); in the initialization of your code. Thanks for the suggestion. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. With Q_DECLARE_METATYPE and without qRegisterMetaType: No warning, slot is called With Q_DECLARE_METATYPE and with qRegisterMetaType: No warning, slot is called. I however have a scenario where I want to declare such an object in qml and transmit it to the c++. Any class or struct that has a public default constructor, a public copy. 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 () <<. 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. To use the type T in queued signal and slot connections, qRegisterMetaType<T>() must be called before the first connection is established. It would look something like this: Q_DECLARE_METATYPE (MyNamespace::MyClass::MyEnum) However, the Q_DECLARE_METATYPE macro would expand to the following call to qRegisterMetaType: qRegisterMetaType< MyNamespace::MyClass::MyEnum > ("MyNamespace::MyClass::MyEnum",. 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. the type name must be specified without the class, as in. Any class or struct that has a public default constructor, a public copy. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. To register. When using signals and slots with multiple threads, see Signals and Slots Across Threads. Here my test code and example:但是如何传递一个程序员自定义的结构体？ 1）在定义结构体之后，要调用Q_DECLARE_METATYPE，向QT声明这个结构体 2）在main. You should use qmlRegisterType function for that. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. 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. 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. Don't use Q_DECLARE_METATYPE and qRegisterMetaType for your QObject enum. Avoid having to qRegisterMetaType (pointer. QtCore. I read on documentation that Q_DECLARE_METATYPE makes available type to QVariant, for example (I got it from documentation): @ struct MyStruct { int i;. Hello Ladies and Gentlemen. Yes, templated types can be used in Qt signal/slots. type() typeName() PySide6. As a result, if the library connects a D-Bus signal to a slot with a signature "void mySlot (MyType)", it is. That. Consider the specific case of qRegisterMetaType. But this is all useless if you are not using templates. But I couldn't register the type because it's a QObject and I don't have access to the implementation to change it. G. See also state() and Creating Custom Qt Types. You can use Q_DECLARE_METATYPE(Widget*) but it is not needed as of Qt. staticMetaObject is of type QMetaObject and provides access to the enums declared with Q_ENUMS. 4 and it seems to work. in your main function or in the constructor of AudioGuiApplication. 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. 1. I want to use my objects as QVariants and for queued connections. I just tried. 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. An alternative would be to wrap shared_ptr<int> in your own class and implement comparison the way you want. Also Q_DECLARE_METATYPE does not register a type, but declares it. Note: it's also safe to call qRegisterMetaType () multiple times. Read and abide by the Qt Code of Conduct. Call qRegisterMetaType() to make type available to non-template based functions, such as the queued signal and slot connections. I can access the property. cpp. hpp which is included in Class1. We all have started by asking questions. I have a few instances of QVector<MyClass> which I want them to be exposed to QScriptEngine. 5 is compiled with GCC 4. 2. I read a bit and it seems that Q_DECLARE_SMART_POINTER_METATYPE is supposed to allow this to work. There's no need to call qRegisterMetaType that many times, once is enough. I tried with and without the qRegisterMetaType<Schedule::TimePairMap>(), with and without Q_DECLARE_METATYPE(Schedule::TimePairMap). void QLocalSocket:: abort ()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. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. For that, I want to declare a. 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. 0. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. Qt is throwing an exception because it doesn't know how to store the shared_ptr onto a QDataStream. PySide6. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. Greetings. One of these plugins uses Q_DECLARE_METATYPE on some types that need to be stored in a QVariant. : Q_DECLARE_METATYPE(MyClass*); That's how Qt handles it with QObject and QWidget. Also, to use type T with the QObject::property () API, qRegisterMetaType () must be. 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. So I tried declaring the following at end of my worker thread class Q_DECLARE_METATYPE(cv::Mat);. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. Type is not registered, please use the Q_DECLARE_METATYPE macro to make it known to Qt's meta-object system. 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. void Message:: registerMetaType {qRegisterMetaType < Message >. See full list on doc. (Make sure 'MyStruct' is registered using qRegisterMetaType (). 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. 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. 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. Also Q_DECLARE_METATYPE does not register a type, but declares it. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. 5 is compiled with GCC 4. e. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. The "traditional" way of doing this is to convert each element to a QVariant, and pass collection as a QVariantList. qRegisterMetaType<FileNodePointer> ("FileNodePointer"); should be called once (in main, constructor etc. 11. You can make them known ( Q_DECLARE_METATYPE ), however you can't register them as QML type. Q_DECLARE_METATYPE. 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. In. To start viewing messages, select the forum that you want to visit from the selection below. Q_DECLARE_METATYPE vs qRegisterMetaType for non global namespace classes. Type is not registered, please use the Q_DECLARE_METATYPE macro to make it known to Qt's meta-object system. To use the type T in queued signal and slot connections, qRegisterMetaType<T>() must be called before the first connection is established. Using Q_ENUM () allows you to retrieve at run-time. 8 and it all went well with a few function changes, except I got QMetaProperty::read: Unable to handle unregistered datatype errors all over. nyaruko. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. Q_DECLARE_METATYPE. 2. You may have to register before you can post: click the register link above to proceed. You may have to register before you can post: click the register link above to proceed. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. Per Qt documentation: To use the type T in QVariant, using Q_DECLARE_METATYPE () is sufficient. Mixing doesn't work but if you always use one or the other it works. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. Q&A for work. 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 class receives a list of variants (wrapping various data) and converts those variants into a binary stream using QDataStream >. Your Matrix type is not copiable, thus you can't use Q_DECLARE_METATYPE on it. qRegisterMetaType vs. As a workaround, I'm using QVariantMap instead of std::map. I need to call the Q_DECLARE_METATYPE() to pass the smart pointer. [since 6. This has been changed, and isNull () now only returns true if the QVariant is empty or contains a nullptr. It associates a type name to a type so that it can be created and destructed dynamically at run-time. To enable creation of objects at run-time, call the qRegisterMetaType() template function to register it with the meta-object system. There's also no need for that typedef, it only makes the code less readable. Is your Q_DECLARE_METATYPE in a header file or an implementation file? Incidentally, there is a mistake in TreeItem.