Read and abide by the Qt Code of Conduct. As you have already found out, you must use Q_DECLARE_METATYPE to make the type known to Qt. To make the custom type. Call qRegisterMetaType() to make type available to non-template based functions, such as the queued signal and slot connections. Detailed Description The QMetaType class manages named types in the meta-object system. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. 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. When data values are exchanged between QML and C++, they are converted by the QML engine to have the correct data types as appropriate for use in QML or C++. See the Custom Type Example for code that demonstrates this. 该类型必须有公有的 构造、析构、复制构造 函数. This function is useful to register typedefs so they can be used by QMetaProperty, or in QueuedConnections. 用qRegisterMetaType对自定义的类型进行注册，就是为了告诉Qt如何去做这些事情。. The QMetaType class manages named types in the meta-object system. Accessing an enum stored in a QVariant. See QMetaType docs for more information. To register. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. 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 (). e. 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. e. By the way, Qt 4. You should use qmlRegisterType function for that. 0. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. By convention, these files are given a . Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. In Qt, you can declare a variable in two ways: 1. h instead ofQVariant x2; x2. That. 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(). See also. However, I cannot figure out how to verify that the included parameter is FACE_UP or FACE_DOWN. To start viewing messages, select the forum that you want to visit from the selection below. 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;. Using the qRegisterMetaType () function The Q_DECLARE_METATYPE () macro is the preferred way to declare a variable in Qt. Share Improve this answer Follow answered Jul 23, 2014 at 15:37. 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. @Daddedebad As @Bonnie says qRegisterMetaType. Then the TYPE ID is saved in local static vairable metatype_id. To make the custom type generally usable with the signals and slots mechanism, we need to perform some extra work. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. It looks like one can register a type more than once, specifying different typenames, i. Call qRegisterMetaType() to register the data type before you establish the connection. Your Matrix type is not copiable, thus you can't use Q_DECLARE_METATYPE on it. qRegisterMetaType () is called to register the TYPE and generate a TYPE ID. As a workaround, I'm using QVariantMap instead of std::map. You can't with Q_GADGETS. 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). void Message:: registerMetaType {qRegisterMetaType < Message >. Teams. Here you can see that the macro expands to nothing. 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. I think you should consider making the signal/slot parameter be const QVector<int>& dataSet. QObject can't be copied and all its descendants can't be copied also. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. 14 vs 5. The QML engine provides built-in support for a. There's no need to call qRegisterMetaType that many times, once is enough. qRegisterMetaType vs. no unexpected garbage. QVariant x2 = QVariant::fromValue( x1); To copy to clipboard, switch view to plain text mode. 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. 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 explicitly don't want to update it on every change to one of the quantities, so they don't. 0. Any class or struct that has a public constructor, a public copy constructor, and a public destructor can be registered. [since 6. . Please note that I do not use Q_DECLARE_METATYPE on purpose because I don't actually need its features (QVariant expansion) right now. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries that are used. 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. Situation. Q_DECLARE_METATYPE QMetaType::type. The following should work: Note that you also have to call qRegisterMetaType<MyMpiMessage> (); before you use the function the first time. To use the type T in QVariant, using Q_DECLARE_METATYPE() is sufficient. There's also no need for that typedef, it only makes the code less readable. Q_DECLARE_METATYPE(MyStruct) Q_DECLARE_METATYPE(MyList) QDBusArgument &operator<<(QDBusArgument &, const MyStruct&);. The logical equivalent of a const T &r (reference to const T) is a const T * const p (const pointer to const T). Now, that Q_DECLARE_METATYPE enables the type for Qt template classes and QVariant. Declare new types with Q_DECLARE_METATYPE () to make them available. Mixing doesn't work but if you always use one or the other it works. Q_GADGET makes a class member, staticMetaObject, available. Of course it's a bug and an odd mistake that Q_DECLARE_METATYPE(QList<QSslError>) is in qsslsocket. Since Qt 5. This also makes the type available for queued. In some cases in Qt 4, it is also necessary to use the qRegisterMetaType method. type() typeName() PySide6. 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. 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. void QAbstractSocket:: abort ()2 Answers. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. The QMetaType class manages named types in the meta-object system. ompiler (repc) generates header files based on an API definition file. Q_DECLARE_METATYPE. 0. QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_REGISTER_METATYPE() and qRegisterMetaType(). rep file extension, short for Replica. I tested your code on Qt 5. QLocalSocket. Q_DECLARE_METATYPE only registers a type in meta type system. First of all you need to declare your custom object for Qt metatype system. 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. To start viewing messages, select the forum that you want to visit from the selection below. Q_DECLARE_METATYPE only registers a type in meta type system. D-Bus offers an extensible type system, based on a few primitive types and associations of them. Ah, sorry, I didn't noticed that part. 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 (). Q_DECLARE_METATYPE(Pkg) and this does not give compile errors, but in my main. 24th July 2010, 09:54 #6. qRegisterMetaType vs. Tried proposed solution using QVariant::fromValue, but kept getting compiler errors of type: . 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 () <<. You may have to register before you can post: click the register link above to proceed. qRegisterMetaType 必须使用该函数的两种情况. Share. 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. 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. This results in access violations when Qt. You may have to register before you can post: click the register link above to proceed. void QLocalSocket:: abort ()The signal "orientationChanged" includes an enum of type "Orientation" to indicate if the card has been turned up or down. This won't work because you can't use qMetaTypeId<> () before Q_DECLARE_METATYPE<>. your custom type definition. That class receives a list of variants (wrapping various data) and converts those variants into a binary stream using QDataStream >. . QVariantList , QString (if the list contains exactly one item) Casting between primitive type (int, float, bool etc. In practice, both the Q_DECLARE_METATYPE() macro and the qRegisterMetaType() template function can be used to register custom types, but qRegisterMetaType() is only required if you need to perform signal-slot communication or need to create and destroy objects of the custom type at run-time. There's no need to call qRegisterMetaType that many times, once is enough. @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). by using qRegisterMetaType(). 3. Yes I tried with qRegisterMetaType, it. 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. 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. The class is used to send arguments over D-Bus to remote applications and to receive them back. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. 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 created a. Don't use Q_DECLARE_METATYPE and qRegisterMetaType for your QObject enum. Workaround: use a class. Use Q_DECLARE_METATYPE (std::string) in one of your headers. I have created an qt bugticket hoping the documentation will be extended. 12. Believing an Question from 2010 and the Qt Documentation, the operator==() doesn't work with custom types. To use the type T in queued signal and slot connections, qRegisterMetaType<T>() must be called before the first connection is established. The file (called a "rep" file) uses a specific (text) syntax to describe the API. I have registered an enumeration type "ClefType" within my header file - this enum is registered with the MetaObject system using the Q_DECLARE_METATYPE and Q_ENUMS macros. 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(). 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. 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. 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. 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. // But the split allows to. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. // But the split allows to. . Q_DECLARE_METATYPE (T) requires the type T to be default-constructable, copiable and destructable. Because Foo is not derived from QObject and QVariant only supports polymorphism for QObject -derived types. 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. And once all of them are updated I'd like the Context object to inform QML to update the view. The file (called a "rep" file) uses a specific (text) syntax to describe the API. Note: it's also safe to call qRegisterMetaType () multiple times. 9k 9 34 52. In the header, after the class declaration, outside the namespace, I've included. @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 () to make type available to non-template based. See also Q_DECLARE_METATYPE() and. QVariantList MyClass::getFooCollection (void) const { QVariantList list; for (const auto& l: fooCollection_) { list. See the Custom Type Example for code. If \c MyStruct is in a namespace, the Q_DECLARE_METATYPE () macro. I tried with and without the qRegisterMetaType<Schedule::TimePairMap>(), with and without Q_DECLARE_METATYPE(Schedule::TimePairMap). qRegisterMetaType() requires also a Q_DECLARE_METATYPE() – dtech. QObject::connect: Cannot queue arguments of type 'MyStruct'. That's created by this macro. 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. Read and abide by the Qt Code of Conduct. QMetaType::type () returns the same ID as qMetaTypeId (), but does a lookup at runtime based on the name of the type. 1. This allows me to use this type in a Q_PROPERTY, this all. 1、自定MyDataType 类型，在这个类型的顶部包含：#include <QMetaType>. cpp. Using the following required me to use Q_DECLARE_METATYPE. 2. due to requirements at my job, I had to revert by build from Qt5. Call qRegisterMetaType() to make type available to non-template based functions, such as the queued signal and slot connections. The other overload around has almost the same form but for the fact that it. 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. 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. {. 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. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. It is a static method, it does not (cannot) change x2. ) is supported. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. e. Detailed Description. I've registered my class with: @Q_DECLARE_METATYPE(MyClass);@ and. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. Without this reference, it compiles just fine. Q_DECLARE_METATYPE. The class in Qt responsible for custom types is QMetaType. 能猜到原因吗？注意看前面 Q_DECLARE_METATYPE() 代码， 对了。类中的成员函数qt_metatype_id中包含对qRegisterMetaType(typeName)的调用: 这儿就是辗转调用了这个带参数的qRegisterMetaType函数: unregisterType(const char *typeName) 函数的作用是取消自己先前注册的某个metatype类型。That is sad. QML Qvariant from custom class. You had to use QMetaType::registerComparators () and the other static register functions in QMetaType to actually make use of that functionality, though. To use the type T in queued signal and slot connections, qRegisterMetaType<T>() must be called before the first connection is established. With Q_DECLARE_METATYPE and without qRegisterMetaType: No warning, slot is called With Q_DECLARE_METATYPE and with qRegisterMetaType: No warning, slot is called. akshatrai91 7 Jan 2021, 06:21. There's no need to call qRegisterMetaType that many times, once is enough. After googling this, I found this correspondence, which was only available through a third party archival site as google. It seems that for a metatype that is a QList<MyClass::MyEnum> I must. 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. For this, a function call (evaluated during runtime) needs to be made, and qRegisterMetatype is the tool for this: qRegisterMetaType<Area>("Area");@julio. This function was introduced in Qt 4. 2）添加声明：利用宏 Q_DECLARE_METATYPE. It associates a type name to a type so that it can be created and destructed dynamically at run-time. EDIT: When you convert your class to QVariant it uses a. This worked very well. Output:Additionally Q_DECLARE_METATYPE and qRegisterMetaType are not purposed to be used for QObject derived classes. Last updated at 2016-07-08 Posted at 2015-11-16. To use the type T in queued signal and slot connections, qRegisterMetaType<T>() must be called before the first connection is established. QMetaType. Well, I certainly overplayed this particular point, but the statement I believe is valid in principle. QLocalSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). Some structure need to be registered to be queued in asynchronous signals using qRegisterMetaType<T>(name), such as signal which passes QVector<int>. SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). View Profile View Forum Posts View Articles Beginner Join Date Nov 2014 Posts 6 Qt products. ), or any other callable, cannot declare a type for use outside of the call site. 3. 5 is compiled with GCC 4. To start viewing messages, select the forum that you want to visit from the selection below. 1. 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. Q&A for work. But I can't see a method to insert myClass into. The following code will work as well: using namespace foo; Q_DECLARE_METATYPE (MyClass) Teams. 1. 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. Returns the internal ID used by QMetaType. QtCore. Any class or struct that has a public default constructor, a public copy constructor, and a. [override virtual] bool QLocalSocket:: waitForBytesWritten (int msecs = 30000) Reimplements:. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries that are used. the type name must be specified without the class, as in. Q_DECLARE_OPAQUE_POINTER (PointerType) This macro enables pointers to forward-declared types (PointerType) to be registered with QMetaType using either Q_DECLARE_METATYPE() or qRegisterMetaType(). E. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. To register VideoMeta you need to call qRegisterMetaType<VideoMeta>(). Consider the specific case of qRegisterMetaType. Do do you register the meta type with the call qRegisterMetaType("your custom meta type")? 1 Reply Last reply Reply Quote 0. You can register a class pointer as the metatype, though. 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. Normally, you would only register the pointer form if your class cannot be copied, as in the case of QObject and derivatives, but. 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. ) summary refs log tree commit diff stats Foo and Foo* are different types and need to be registered separately. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. Read and abide by the Qt Code of Conduct. 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. The ones I am registering for are mostly structs for storing data and just a few simple classes. My workround was to explicitly cast the enum values to int when passing them onto a function requiring a QVariant type, in my case when adding a QComboBox item, and then casting it back to my enum class type at value retrieval. hpp and qRegisterMetaType<quint32>("quint32"); in both the Constructors of Class1 and Class2. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. Call qRegisterMetaType() to make type available to non-template based functions, such as the queued signal and slot connections. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. qt. See also. no unexpected garbage data or the like). Our first stop for registrations always is the macro Q_DECLARE_METATYPE. From the docs: int qRegisterMetaType ( const char * typeName ) Registers the type name typeName to the type T. You can make them known ( Q_DECLARE_METATYPE ), however you can't register them as QML type. Than I did read this copy constructor of derived QT class and the answer by BЈовић. To register a type, it must be declared as a meta-type with the Q_DECLARE_METATYPE() macro, and then registered as in the following example:. We all have started by asking questions. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. Duplicate Question(s):Q_DECLARATIVE_METATYPE in and out; Using EventExport vs. Type is not registered, please use the Q_DECLARE_METATYPE macro to make it known to Qt's meta-object system. That's probably there, as qRegisterMetaType () wouldn't compile otherwise. Q_DECLARE_METATYPE. Update. Current the only supported type info is QML_HAS_ATTACHED_PROPERTIES. Normally, you would only register the pointer form if your class cannot be copied, as in the case of QObject and derivatives, but. namespace CCS { Q_DECL_EXPORT Q_NAMESPACE. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. QML_DECLARE_TYPE. See also state() and Creating Custom Qt Types. 【2】使用方法（声明 和 注册自定义数据类型）. It is still giving the error"QObject::connect: Cannot queue arguments of type 'quint32&' (Make sure 'quint32&' is registered using. Hello, Can someone tell me about how to register a metatype in pyqt5. nyaruko. Q&A for work. 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. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. So in your case you need to declare. Re: How to use Q_DECLARE_METATYPE. This function was introduced in Qt 6. Since Qt 5. 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. Even though we do not intend. // to be declared somewhere Q_DECLARE_METATYPE(std::string); // to be invoked at the beginning of program qRegisterMetaType<std::string>(); Without type registration Qt doesn't know how to do. rep file extension, short for Replica. I haven't used that module yet but one thing you should do is remove the string argument from your qRegisterMetaType calls. 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. It associates a type name to a type so that it can be created and destructed dynamically at run-time. 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. From the QVariant::value documentation: If the QVariant contains a pointer to a type derived from QObject then T may be any QObject type. 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. Connect and share knowledge within a single location that is structured and easy to search. The QMetaType class manages named types in the meta-object system. Enum has been moved from outside of the class to inside of it. 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. 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. I just tried. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. Declare new types with Q_DECLARE_METATYPE () to make them available. . w/out GUI module you wouldn't have any of those types available). 2. You can also use QMetaEnum::fromType() to get the QMetaEnum. To make the custom. One of these plugins uses Q_DECLARE_METATYPE on some types that need to be stored in a QVariant. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries that are used. Call qRegisterMetaType() to register the data type before you establish the connection. See the Qt D-Bus Type System page for more information on the type system. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. 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 (). g. Reply Quote. J 1 Reply Last reply Reply Quote 0. I simplified the code quite a bit and the problem went away. Some structure need to be registered to be queued in asynchronous signals using qRegisterMetaType<T>(name), such as signal which passes QVector<int>. hi, I always after application running, receive debug text of: QObject::connect: Cannot queue arguments of type 'MyStruct'. 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. To start viewing messages, select the forum that you want to visit from the selection below. Q_DECLARE_METATYPE(MyClass*); That's how Qt handles it with QObject and QWidget. QVariant v = QVariant::fromValue<cMyClass>(MyObject); However, as soon as I use Q_DECLARE_METATYPE, I get errors about using a deleted function. Re: How to use Q_DECLARE_METATYPE. The logical equivalent of a const T &r (reference to const T) is a const T * const p (const pointer to const T). QMetaType Synopsis Functions def __eq__ (b). Any class or struct that has a public constructor, a public copy constructor, and a public destructor can be registered. 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. When these files are processed by repc, repc generates both. qRegisterMetaType vs. Actually, they are declared, but in a private section with the macro Q_DISABLE_COPY(). F. 7. You may have to register before you can post: click the register link above to proceed. wysota. One of these plugins uses Q_DECLARE_METATYPE on some types that need to be stored in a QVariant. Sorted by: 1. 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. Although I'm. Is your feature request related to a problem? No, it's an improvement Please describe. 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. 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.