You pass around pointers instead. 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. before saveload operation would happen. The class in Qt responsible for custom types is QMetaType . QVariantList , QString (if the list contains exactly one item) Casting between primitive type (int, float, bool etc. Jun 13, 2021 at 19:37. To register VideoMeta you need to call qRegisterMetaType<VideoMeta>(). . " and: "Warning: This function is useful only for registering an alias (typedef) for every other use case Q_DECLARE_METATYPE and qMetaTypeId() should be used instead. This allows me to use this type in a Q_PROPERTY, this all. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. 基本理解. 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. In short, I get following error: QObject::connect: Cannot queue arguments of type 'cv::Mat' (Make sure 'cv::Mat' is registered using qRegisterMetaType (). 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. QMetaType registerNormalizedTypedef normalizedTypeName, type: metaType ); return. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. 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。. e. 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. QLocalSocket::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. 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. h) of the derived class. Believing an Question from 2010 and the Qt Documentation, the operator==() doesn't work with custom types. Here you can see that the macro expands to nothing. Hope it. Learn more about Teams Declaring a meta type. 2 Answers. 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. Than I did read this copy constructor of derived QT class and the answer by BЈовић. I think it would be great if we could run requests in a QThread, but right now it's not possible because the r. 2. Even though we do not intend. The "traditional" way of doing this is to convert each element to a QVariant, and pass collection as a QVariantList. Consider the specific case of qRegisterMetaType. qRegisterMetaType is also called in the class constructor. See also state() and Creating Custom Qt Types. 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. This object can then be passed from QML to C++ via Q_INVOKABLE. This now makes it possible for Message values to be stored in QVariant objects and retrieved later. This has been changed, and isNull () now only returns true if the QVariant is empty or contains a nullptr. 4] QString QWebSocket:: subprotocol const. I haven't used that module yet but one thing you should do is remove the string argument from your qRegisterMetaType calls. 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. Any class or struct that has a public default constructor, a public copy constructor, and a. But this is all useless if you are not using templates. Compares this QVariant with v and returns true if they are equal;. Share Improve this answer Follow answered Jul 23, 2014 at 15:37. complains that the metatype isn't registered. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. PySide6. By the way, Qt 4. ", which suggests it is only for classes and structs. // But the split allows to. 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 (). The QMetaType class manages named types in the meta-object system. The ENUM type. Now, that Q_DECLARE_METATYPE enables the type for Qt template classes and QVariant. To use the type T in QVariant, using Q_DECLARE_METATYPE() is sufficient. Returns the metatype of the parameter at the given index. 4. 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. 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). Q_DECLARE_METATYPE(TYPEDEF) Q_DECLARE_METATYPE(TYPEDEF) mainwindow. Has anyone else encountered this?See also qRegisterMetaType(). The file (called a "rep" file) uses a specific (text) syntax to describe the API. You don't pass around copies of QObject derived types because it is not copyable. J. Although I'm. This is by design. I read on documentation that Q_DECLARE_METATYPE makes available type to QVariant, for example (I got it from documentation): @ struct MyStruct { int i;. I want to use drag-and-drop to drag a QTreeWidgetItem that has std::shared_ptr user data. qRegisterMetaType you'll need if creating objects by class name dynamically, and it seems for queued connections,. The docs only talk about class or struct with public default constructor, copy constructor and. The QMetaType class manages named types in the meta-object system. . . statement to the header file containing. However, when attempting to compile QCustomPlot in a project using "QT += 3dinput" in its . QML_DECLARE_TYPE. A separate point for your own benefit. 2 Answers. Q_DECLARE_METATYPE. Thanks for the suggestion. Q_DECLARE_METATYPE only registers a type in meta type 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. Ah, sorry, I didn't noticed that part. Q_DECLARE_METATYPE is required to store type with QVariant, those two are required to register object's "big three" to manage it as resource and its serialization methods. Thank you Volker, I had a couple of problems I forgot about the Q_DECLARE_METATYPE(myType); and I don't' think I was never consistent with the global scope specifier. Q_DECLARE_METATYPE accepts objects with public constructor, copy constructor and destructor. QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_REGISTER_METATYPE() and qRegisterMetaType(). The QMetaType class manages named types in the meta-object system. Sorted by: 3. Yes, templated types can be used in Qt signal/slots. no unexpected garbage. As G. QList of Custom Objects. due to requirements at my job, I had to revert by build from Qt5. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. Normally, you would only register the pointer form if your class cannot be copied, as in the case of QObject and derivatives, but. To call qRegisterMetaType (), you still need to use Q_DECLARE_METATYPE (). Once they're known you can use them, but you can't create them on the QML side. no unexpected garbage data or the like). The code compiles and runs ok. It will return the same result if it was called before. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. Returns the internal ID used by QMetaType. このケースでも、Q_DECLARE_METATYPE(QSharedPointer<MyObject>)の宣言と、qRegisterMetatype<QSharedPointer<MyObject>>()の呼び出しが必要になる。 上のサンプルでは、同じsignalに対して2回connectを実行している。 The correct syntax is Q_DECLARE_METATYPE (std::string) without the ;. You may have to register before you can post: click the register link above to proceed. class Test : public QWidget { Q_OBJECT public: Test(); signals: public slots: void setAppData(QList<QIcon> icons, QStringList names, QStringList versions, QStringList publishers, QString installLocation, QStringList uninstallLocations); private: }; Q_DECLARE_METATYPE(QIcon) The same issue is still present. cpp. This function was introduced in Qt 4. Any class or struct that has a public default constructor, a public copy. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. I only care about runtime instantiation. 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. D-Bus offers an extensible type system, based on a few primitive types and associations of them. Here you can see that the macro expands to nothing. 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: This now makes it possible for Message values to be stored in QVariant objects and retrieved later. To start viewing messages, select the forum that you want to visit from the selection below. Any idea what I'm missing please? BTW, no problem at all using Schedule in QMetaProperty or QVariant. Your Matrix type is not copiable, thus you can't use Q_DECLARE_METATYPE on it. Use Q_DECLARE_METATYPE (std::string) in one of your headers. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. Make a typedef for QSharedPointer<UserDataType>, and use both Q_DECLARE_METATYPE as well as qRegisterMetaType () to register it for use. void Message:: registerMetaType {qRegisterMetaType < Message >. the type name must be specified without the class, as in. cpp. So you can call it from your constructor. 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. 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. I have a few instances of QVector<MyClass> which I want them to be exposed to QScriptEngine. G. 2、在类型定义完成后，加入声明：Q_DECLARE_METATYPE (MyDataType); 3、在main ()函数中. h. To enable using the type in queued signals and such, there also needs to be a corresponding call: qRegisterMetaType<foo::FooState>(); Question. Improve this answer. I just tried. 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。. namespace CCS { Q_DECL_EXPORT Q_NAMESPACE. I read on documentation that Q_DECLARE_METATYPE makes available type to QVariant, for example (I got it from documentation): @ struct MyStruct { int 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. First of all you need to declare your custom object for Qt metatype system. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. int videoSourceMetaTypeId = qRegisterMetaType< VideoSource > ();Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. The third without Q_DECLARE_METATYPE. You may have to register before you can post: click the register link above to proceed. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. e. The. 3 to Qt4. Thus you need to use the runtime check QMetaType::type (). 1 Answer. in a header file and call @qRegisterMetaType<std::unique_ptr<Thing>> ();@ before your signal and slots are used. Secondly, your linker (MSVC) complains that it can't find the metaObject for your ErrorHandler enum, which is normal as it is not exported from the. QMetaType::type () returns the same ID as qMetaTypeId (), but does a lookup at runtime based on the name of the type. View Profile View Forum Posts View Articles Beginner Join Date Nov 2014 Posts 6 Qt products. S 1 Reply Last reply Reply Quote 0. But I couldn't register the type because it's a QObject and I don't have access to the implementation to change it. The issue here is that Q_OBJECT forbids the copy and assignment constructors. [virtual] QAbstractSocket:: ~QAbstractSocket Destroys the socket. 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. Then after some time, we can begin answering them. See also. 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. You may have to register before you can post: click the register link above to proceed. } 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. QObject::connect: Cannot queue arguments of type 'MyStruct'. qRegisterMetaType() docs say: Any class or struct that has a public constructor, a public copy constructor, and a public destructor can be registered. And once all of them are updated I'd like the Context object to inform QML to update the view. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries that are used. e. Call qRegisterMetaType<std::string> (); in the initialization of your code. @SGaist Yes, I am using it with QVariant, mostly with QSettings to save and retrieve data easily by overriding QDataStream operators. 如果非QMetaType内置类型要. 0. The following should work: Note that you also have to call qRegisterMetaType<MyMpiMessage> (); before you use the function the first time. But I really would like to know the correct way to solve this problem; one where it is not possible to modify. 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. . From the QVariant::value documentation: If the QVariant contains a pointer to a type derived from QObject then T may be any QObject type. qRegisterMetaType vs. 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. This also makes the type available for queued. To use the type T in queued signal and slot connections, qRegisterMetaType () must be called before the first connection is established. Read and abide by the Qt Code of Conduct. Any class or struct that has a public default constructor, a public copy. 1. 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. h" class Context : public QObject { Q_OBJECT Q_PROPERTY (MyGadget* gadget READ gadget CONSTANT) public: explicit Context () : QObject {nullptr} { } MyGadget* gadget () { return &_gadget; } private. The default access for a class is private, so that Container* data();. 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. Q_DECLARE_METATYPE QMetaType::type. To use the type T in queued signal and slot connections, qRegisterMetaType<T>() must be called before the first connection is established. I pass the MyClass pointer to the streaming operator and only stream things like QString, QPointF, etc. 1. " Currently I have no UI implemented (yet!). 2. Re: How to use Q_DECLARE_METATYPE. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. Jul 9, 2017 at 21:51. 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 () <<. 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. 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. I can access the property. g. So I tried declaring the following at end of my worker thread class Q_DECLARE_METATYPE(cv::Mat);. 幸哉~ Qt是支持自定义信号，且自定义信号可以发送自定义数据类型的对象。. call qRegisterMetaType with the name specified, else reading properties. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. Connect and share knowledge within a single location that is structured and easy to search. 0. akshatrai91 7 Jan 2021, 06:21. See also state() and Creating Custom Qt Types. Now, that Q_DECLARE_METATYPE enables the type for Qt template classes and QVariant. I guess it's the qRegisterMetaType () call itself that's missing. There's no need to call qRegisterMetaType that many times, once is enough. Using the qRegisterMetaType () function The Q_DECLARE_METATYPE () macro is the preferred way to declare a variable in Qt. call qRegisterMetaType() to register the data type before you establish the connection. J 1 Reply Last reply Reply Quote 0. Obviously then you would not do registerComparator (). container. E. the type name must be specified without the class, as in. 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 (). There's also no need for that typedef, it only makes the code less readable. Make sure you call it from within a method. Sorted by: 2. Call qRegisterMetaType () to make type available to non-template based functions. 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. Secondly, your linker (MSVC) complains that it can't find the metaObject for your ErrorHandler enum, which is normal as it is not exported from the. I believe this is related to the fact that. ompiler (repc) generates header files based on an API definition file. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. I meet a qt metatype issue. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. This worked very well. Note that you are technically lying to the meta type system. So I don't stream the pointer itself just copy the properties and set them to a new created pointer object. The object it returns should also be a member of the factory class. // copiable, C++98 brace-initializable, etc. EDIT: When you convert your class to QVariant it uses a. Output:Additionally Q_DECLARE_METATYPE and qRegisterMetaType are not purposed to be used for QObject derived classes. To start viewing messages, select the forum that you want to visit from the selection below. It must appear in a code block. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. i. goocreations 12 Mar 2013, 07:22. Our first stop for registrations always is the macro Q_DECLARE_METATYPE. QLocalSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). 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. 1. This results in access violations when Qt. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. I think you should consider making the signal/slot parameter be const QVector<int>& dataSet. It does not say anything about registering the type. QMetaType::type () is a bit slower, but compilation succeeds if a type is not registered. The macro will register your variable with the Qt Meta-Object System, which will allow you to. Make sure you call it from within a method. @Q_DECLARE_METATYPE (std::unique_ptr<Thing>);@. 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. This won't work because you can't use qMetaTypeId<> () before Q_DECLARE_METATYPE<>. To use the type T in queued signal and slot connections, qRegisterMetaType () must be called before the first connection is established. 7. const EventExport& in signal and slot profiles; Sending empty EventExport in prepareExport() so emit has no/low data amount; Checking connect statement (always returns true) Having qDebug() in prepareExport() and signal always appears to be emitted; Calling emit right. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. Using the Q_DECLARE_METATYPE () macro 2. Also you may need to use qRegisterMetaType function. Q_DECLARE_METATYPE ( blabla* ) Also qRegisterMetaType<T> () is only required for sending your object through queued signal/slot connections. To use the type T in queued signal and slot connections,. // 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. Any class or struct that has a public default constructor, a public copy. h in the translation unit where you have that line. 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. To make the custom. Additional types can be registered using qRegisterMetaType() or by calling registerType(). I read a bit and it seems that Q_DECLARE_SMART_POINTER_METATYPE is supposed to allow this to work. 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. ) QObject::connect: Cannot queue arguments of type 'QVector<int>'. So you can call it from your constructor. M. hi, I always after application running, receive debug text of: QObject::connect: Cannot queue arguments of type 'MyStruct'. I thought there was a bug with QMetaType or Q_DECLARE_METATYPE. Re: How to use Q_DECLARE_METATYPE. See also state() and Creating Custom Qt Types. 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 think you need to add an explicit export/import directive to the QT_NAMESPACE macro. It associates a type name to a type so that it can be created and destructed dynamically at run-time. qRegisterMetaType 必须使用该函数的两种情况. rep file extension, short for Replica. It seems that for a metatype that is a QList<MyClass::MyEnum> I must. Therefore I want to use Q_DECLARE_METATYPE (My_Item) and from the documentation I learned that I need a public copy constructor. This macro is used to specialise the template class QMetaTypeId with typename TYPE, in which, a static member function qt_metatype_id () is defined. 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. See also isRegistered () and Q_DECLARE_METATYPE (). See also. Macros Detailed Description The QMetaType class manages named types in the meta-object system. 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. struct StandardData { int EmpId; QString Name; }; Q_DECLARE_METATYPE (StandardData) Additionally, you might need to call qRegisterMetaType. To start viewing messages, select the forum that you want to visit from the selection below. As the docs state: Declare new types with Q_DECLARE_METATYPE () to make them available to QVariant and other template-based functions. genC last edited by . Q_DECLARE_METATYPE. Q_DECLARE_METATYPE(MyStruct) Q_DECLARE_METATYPE(MyList) QDBusArgument &operator<<(QDBusArgument &, const MyStruct&);. 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. Q_DECLARE_METATYPE QMetaType::type. Call qRegisterMetaType() to make type available to non-template based functions, such as the queued signal and slot connections. There's no compile time error, but when I run. So in your case you need to declare. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). h instead ofQVariant x2; x2. Obviously, a call to qRegisterMetaType<T>(. Note that you are technically lying to the meta type system. qRegisterMetaType vs. Jun 13, 2021 at 19:37. 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. Registers the type name . The QML engine provides built-in support for a. In that case, I think you need to register them. Then you should register your object to use it with QML. So using a QString as the type of a Q_PROPERTY only works because it has special built-in support in the QML engine. 16. But because QUuid stores its content as a QByteArray which is already supported by QVariant, you. 4] QString QWebSocket:: subprotocol const. Accessing an enum stored in a QVariant. So I played around, copied the original macro and adapted it a bit: @. 12. Qt Remote Objects Compiler. 步骤： (以自定义MyDataType类型为例）. Note that you are technically lying to the meta type system. QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). The Q_DECLARE_METATYPE() macro and qRegisterMetaType() function documentation contain more detailed information about their uses and limitations. 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. Good workaround: you may register your type with Q_DECLARE_METATYPE ( IBase * ) macro and wrap your. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. But at run time, I got below error:1 Answer. 4 which does not support all C++11 features. pro file, several errors appear referencing the QMouseEvent and QWheelEvent classes. I need to call the Q_DECLARE_METATYPE() to pass the smart pointer. However Q_DECLARE_METATYPE () is a bit more complicated. In Qt, you can declare a variable in two ways: 1. @SGaist Yes, I am using it with QVariant, mostly with QSettings to save and retrieve data easily by overriding QDataStream operators. Q&A for work. This version of the function is to register alias types. See also state() and Creating Custom Qt Types. If the type was not declared with Q_DECLARE_METATYPE (), compilation will fail. qt. jsulm Lifetime Qt Champion @shivaVMC last edited by . See also Q_DECLARE_METATYPE() and. Re: Qt warning of type conversion already registered Originally. no I didn't, do I need to put in the file generated by repc or I can put it anywhere ? – Houss_gc. 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. Custom Type Qlist and Scope. 1、自定MyDataType 类型，在这个类型的顶部包含：#include <QMetaType>. 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:. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. Type is not registered, please use the Q_DECLARE_METATYPE macro to make it known to Qt's meta-object system. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. 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. qRegisterMetaType vs. 该类型必须有公有的 构造、析构、复制构造 函数. The. You may have to register before you can post: click the register link above to proceed. It is meant to be put in a header where the given type is declared.