3. This makes them suitable for use with both static properties declared using the Q_PROPERTY() macro in class definitions and dynamic properties created at run-time. Q_DECLARE_METATYPE. {. It will return the same result if it was called before. To register. 2. Email This BlogThis! Share to Twitter Share to Facebook Share to Pinterest. Returns the metatype of the parameter at the given index. Even though we do not intend. With Q_DECLARE_METATYPE and without qRegisterMetaType: No warning, slot is called With Q_DECLARE_METATYPE and with qRegisterMetaType: No warning, slot is called. Learn more about Teams Declaring a meta type. I can access the property. I have declared all the types with Q_DECLARE_METATYPE, Q_OBJECT and the properties with Q_PROPERTY with the proper getters and setters. I my real world application Context holds a large number of physical quantities (masses, forces, velocities,. 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. 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. Qt is throwing an exception because it doesn't know how to store the shared_ptr onto a QDataStream. I want to use drag-and-drop to drag a QTreeWidgetItem that has std::shared_ptr user data. qRegisterMetaType<signed long long>() - do nothing. It associates a type name to a type so that it can be created and destructed dynamically at run-time. Q_DECLARE_METATYPE(Pkg) and this does not give compile errors, but in my main. Detailed Description. Now, in your registerTypes function, it should be registered like this: qRegisterMetaType<AccReal > ("data::AccReal"); In other words, the typeName string must match exactly the type of the signal argument as it is written there. " Yet types like QVariantMap are themself typedefs. See full list on doc. If the type was not declared with Q_DECLARE_METATYPE (), compilation will fail. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. 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. Now I want to read this property with Qt's meta object system. 1. 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. Got a similar example working without explicitly calling qRegisterMetaType() just by removing the semicolon from the line Q_DECLARE_METATYPE(StateMachine::state) – user666412 Sep 21, 2015 at 14:17Additional types can be registered using qRegisterMetaType() or by calling registerType(). ) What I'm trying to do is send a signal containing two cv::Mat images from a QThread to the main thread, so that I can display the output. ) What I'm trying to do is send a signal containing two cv::Mat images from a QThread to the main thread, so that I can display the output. 0. Q_DECLARE_METATYPE(TYPEDEF) Q_DECLARE_METATYPE(TYPEDEF) mainwindow. QLocalSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). Q_DECLARE_METATYPE(MyStruct) Q_DECLARE_METATYPE(MyList) QDBusArgument &operator<<(QDBusArgument &, const MyStruct&);. Then you should register your object to use it with QML. Our first stop for registrations always is the macro Q_DECLARE_METATYPE. jsulm Lifetime Qt Champion @shivaVMC last edited by . Unsure if my idea would work, I created a DataPoint class marked with Q_GADGET with three properties defined using Q_PROPERTY. See also state() and Creating Custom Qt Types. Re: How to use Q_DECLARE_METATYPE. 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. 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. Research The QMetaType class manages named types in the meta-object system. 1 Answer. in a header file and call @qRegisterMetaType<std::unique_ptr<Thing>> ();@ before your signal and slots are used. The ones I am registering for are mostly structs for storing data and just a few simple classes. Q_DECLARE_METATYPE vs qRegisterMetaType for non global namespace classes. QMetaType::type () returns the same ID as qMetaTypeId (), but does a lookup at runtime based on the name of the type. 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. 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. If you ever wondered what does Q_DECLARE_META_TYPE or qRegisterMetaType do and when to use (or not to use) them, read on. ), or any other callable, cannot declare a type for use outside of the call site. When these files are processed by repc, repc generates both Source and Replica header files. However, it does appear (at least to me) that you're trying to debug a release build of the application. All Qt Overviews. To make the custom type generally usable with the signals and slots mechanism, we need to perform some extra work. 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. And once all of them are updated I'd like the Context object to inform QML to update the view. 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. To use the type T in queued signal and slot connections, qRegisterMetaType<T>() must be called before the first connection is established. 23k 10 10 gold. This function was introduced in Qt 6. QMetaType. This function is typically used together with construct () to perform low-level management of the memory used by a type. Step 1 (mark for MOC), build some QObjects That pattern uses Q_PROPERTY and Q_OBJECT and the MoC tool. :) QApplication is the root QObject of the program and its full initialization is required before anything can practically be done with anything else. 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. You may have to register before you can post: click the register link above to proceed. 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. Has anyone else encountered this?See also qRegisterMetaType(). // But the split allows to. Call qRegisterMetaType() to register the data type before you establish the connection. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. You don't pass around copies of QObject derived types because it is not copyable. 3 Answers Sorted by: 13 "qRegisterMetaType" is a function. 基本理解. QList<AnotherObject*> has of course been registered with Q_DECLARE_METATYPE and qRegisterMetaType(). Q_DECLARE_METATYPE, as pointed out by @SingerOfTheFall, would register template based type into QVariant (so it can be retrieved using qvariant_cast<T>()). Using the macro directly turned out to be impossible. I want to use drag-and-drop to drag a QTreeWidgetItem that has std::shared_ptr user data. See also. hpp which is included in Class1. 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. (Make sure 'QVector<int>' is. So I don't stream the pointer itself just copy the properties and set them to a new created pointer object. 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. multithreaded software and I am getting the warning says: (Make sure 'QVector<int>' is registered using qRegisterMetaType (). In that case, I think you need to register them. This allows me to use this type in a Q_PROPERTY, this all. In my own code, I use Q_DECLARE_METATYPE for classes I want to store. I tested your code on Qt 5. The. The problem of owner ship of the memory is avoided. You may have to register before you can post: click the register link above to proceed. Data Type Conversion Between QML and C++. 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. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. ", which suggests it is only for classes and structs. It is meant to be put in a header where the given type is declared. 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. Enumerations that are declared with Q_ENUM have their QMetaEnum registered in the enclosing QMetaObject. The correct syntax is Q_DECLARE_METATYPE (std::string) without the ;. Of course it's a bug and an odd mistake that Q_DECLARE_METATYPE(QList<QSslError>) is in qsslsocket. I'm confused by this error, as the documentation states (emphasis mine): Returns the meta type id of type T at compile time. You may have to register before you can post: click the register link above to proceed. Q_DECLARE_METATYPE. e. To copy to clipboard, switch view to plain text mode. qRegisterMetaType you'll need if creating objects by class name dynamically, and it seems for queued connections,. namespace CCS { Q_DECL_EXPORT Q_NAMESPACE. staticMetaObject is of type QMetaObject and provides access to the enums declared with Q_ENUMS. 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. typedef QVector<QSharedPointer<Tester> > TestPointerVector;. This results in access violations when Qt. 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. That always worked in Qt4, but in Qt5 I get the following error: @error: specializing member ‘::qRegisterMetaType<Subclass>’ requires ‘template<>’ syntax@. You may have to register before you can post: click the register link above to proceed. QLocalSocket. 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. 该类型必须有公有的 构造、析构、复制构造 函数. But this is all useless if you are not using templates. Current the only supported type info is QML_HAS_ATTACHED_PROPERTIES. 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. 3 to Qt4. 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. Now you have a valid QObject. e. Connect and share knowledge within a single location that is structured and easy to search. There's also no need for that typedef, it only makes the code less readable. Q_DECLARE_METATYPE (std::string) Quoting Qt Doc. It associates a type name to a type so that it can be created and destructed dynamically at run-time. Thus you need to use the runtime check QMetaType::type (). 4. 1. 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'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. QtNetwork. Share Improve this answer Follow answered Jul 23, 2014 at 15:37. 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. Note: This function is thread-safe. Obviously, a call to qRegisterMetaType<T>(. I am also using some in queued signal and slot connections. Last updated at 2016-07-08 Posted at 2015-11-16. 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. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. Therefore I want to use Q_DECLARE_METATYPE (My_Item) and from the documentation I learned that I need a public copy constructor. Trying to register std::map<non_template_type_1,non_template_type_2> with Q_DECLARE_METATYPE() results in compilation failure and apparently is not supported. You can also use QMetaEnum::fromType() to get the QMetaEnum. See QMetaType docs for more information. Q_DECLARE_METATYPE only registers a type in meta type system. A separate point for your own benefit. QVariant::fromValue () returns a QVariant. Connect and share knowledge within a single location that is structured and easy to search. The class in Qt responsible for custom types is QMetaType . It associates a type name to a type so that it can be created and destructed dynamically at run-time. 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",. 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. G. 4. 1. If you only want to store pointer to Foo with the metatype system, then use qRegisterMetaType<Foo *> ();. The "traditional" way of doing this is to convert each element to a QVariant, and pass collection as a QVariantList. Obviously then you would not do registerComparator (). One way to work around this is for example having a helper class (singleton or context property) with. Jun 13, 2021 at 19:37. I am also using some in queued signal and slot connections. So I tried declaring the following at end of my worker thread class Q_DECLARE_METATYPE(cv::Mat);. 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. 如果非QMetaType内置类型要. Some structure need to be registered to be queued in asynchronous signals using qRegisterMetaType<T>(name), such as signal which passes QVector<int>. I thought there was a bug with QMetaType or Q_DECLARE_METATYPE. This now makes it possible for Message values to be stored in QVariant objects and retrieved later. 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. Use Q_DECLARE_METATYPE (std::string) in one of your headers. There's no need to call qRegisterMetaType that many times, once is enough. private: AnotherQGadgetClass test_; } Q_DECLARE_METATYPE(QGadgetClass) I am trying to access Q_GADGET from QML classic way like accessing a Q_OBJECT , but the setters are not called. You may have to register before you can post: click the register link above to proceed. Also Q_DECLARE_METATYPE does not register a type, but declares it. Call qRegisterMetaType() to make type available to non-template based functions, such as the queued signal and slot connections. Step 1 (mark for MOC), build some QObjects That pattern uses Q_PROPERTY and Q_OBJECT and the MoC tool. SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). 2. 2. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. qRegisterMetaType vs. 1 Answer. This object can then be passed from QML to C++ via Q_INVOKABLE. The file (called a "rep" file) uses a specific (text) syntax to describe the API. . So my first idea:. qRegisterMetaType vs. This replaces the now-deprecated Q_ENUMS and will automatically register the metatype. Declare new types with Q_DECLARE_METATYPE () to make them available to. 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. See also state() and Creating Custom Qt Types. @SGaist Yes, I am using it with QVariant, mostly with QSettings to save and retrieve data easily by overriding QDataStream operators. Then you should register your object to use it with QML. Assuming base and derived are Q_GADGETs you want to get a static member. Call qRegisterMetaType() to make type 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. Call qRegisterMetaType() to register the data type before you establish the connection. 5 is compiled with GCC 4. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. 2 Answers. The reasoning is found in the discussion on Identity vs Value on the Qt Object Model page. The issue here is that Q_OBJECT forbids the copy and assignment constructors. 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. Q&A for work. This fixed the issue. QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_REGISTER_METATYPE() and qRegisterMetaType(). Using the qRegisterMetaType () function The Q_DECLARE_METATYPE () macro is the preferred way to declare a variable in Qt. It manages an insane amount of static variables and sets a static global pointer of. With Q_DECLARE_METATYPE and without qRegisterMetaType: No warning, slot is called With Q_DECLARE_METATYPE and with qRegisterMetaType: No warning, slot is called. There's no need to call qRegisterMetaType that many times, once is enough. This is by design. 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. I store them in QVariant :. void QAbstractSocket:: abort ()2 Answers. See also state() and Creating Custom Qt Types. Avoid having to qRegisterMetaType (pointer vs reference), concern about const. [override virtual] bool QLocalSocket:: waitForBytesWritten (int msecs = 30000) Reimplements:. pro file, several errors appear referencing the QMouseEvent and QWheelEvent classes. Returns the internal ID used by QMetaType. From the QVariant::value documentation: If the QVariant contains a pointer to a type derived from QObject then T may be any QObject type. To start viewing messages, select the forum that you want to visit from the selection below. See also Thread Support in Qt, QObject::connect(), qRegisterMetaType(), and Q_DECLARE_METATYPE(). 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. 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. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. However, as you need the type to be. Any class or struct that has a public default constructor, a public copy constructor, and a. Then the TYPE ID is saved in local static vairable metatype_id. You may have to register before you can post: click the register link above to proceed. Teams. Share. If you want both, then register both. Note that for enum types, you no not even need to call qRegisterMetaType () in these cases. This object can then be passed from QML to C++ via. Registered enumerations are automatically registered also to the Qt meta type system, making them known to QMetaType without the need to use Q_DECLARE_METATYPE(). You could try using registerConverter () to allow implicit conversion of the shared_ptr<int> to a regular int, and compare them that way. To use the type T in queued signal and slot connections, qRegisterMetaType<T>() must be called before the first connection is established. @Wieland Thanks. Q_DECLARE_METATYPE(TYPEDEF) Q_DECLARE_METATYPE(TYPEDEF) mainwindow. rep file extension, short for Replica. I only care about runtime instantiation. 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. 4 which does not support all C++11 features. Please note that I do not use Q_DECLARE_METATYPE on purpose because I don't actually need its features (QVariant expansion) right now. Type is declared with Q_DECLARE_METATYPE and registered with qRegisterMetaType. QObject::connect: Cannot queue arguments of type 'MyStruct'. See also Q_DECLARE_METATYPE() and. 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. Read and abide by the Qt Code of Conduct. QDBusArgument is the central class in the Qt D-Bus type. This won't work because you can't use qMetaTypeId<> () before Q_DECLARE_METATYPE<>. Now, that Q_DECLARE_METATYPE enables the type for Qt template classes and QVariant. Gerald Gerald. You can register a class pointer as the metatype, though. So in your case you need to declare. There is no way to add support for more of these value types like std::string (*). See also Thread Support in Qt, QObject::connect(), qRegisterMetaType(), and Q_DECLARE_METATYPE(). See the Custom Type Example for code. What worries me is that. int videoSourceMetaTypeId = qRegisterMetaType< VideoSource > ();Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. 4 which does not support all C++11 features. To start viewing messages, select the forum that you want to visit from the selection below. You should use qmlRegisterType function for that. The object it returns should also be a member of the factory class. I have created an qt bugticket hoping the documentation will be extended. 0. The class in Qt responsible for custom types is QMetaType. e. Follow. [since 6. Q_DECLARE_METATYPE only registers a type in meta type system. 【2】使用方法（声明 和 注册自定义数据类型）. See also. Returns the internal ID used by QMetaType. In. This function was introduced in Qt 4. qRegisterMetaType() requires also a Q_DECLARE_METATYPE() – dtech. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. The ENUM type. What is(are) the good place(s) to put the qRegisterMetaType call? I obviously don't want any expllicit. However Q_DECLARE_METATYPE () is a bit more complicated. cpp. I tried with and without the qRegisterMetaType<Schedule::TimePairMap>(), with and without Q_DECLARE_METATYPE(Schedule::TimePairMap). 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. It seems that for a metatype that is a QList<MyClass::MyEnum> I must. 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. in a header file and call @qRegisterMetaType<std::unique_ptr<Thing>> ();@ before your signal and slots are used. Call qRegisterMetaType<std::string> (); in the initialization of your code. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. The other overload around has almost the same form but for the. 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. For pointer types, it also requires that the pointed to type is fully defined. by using qRegisterMetaType(). x however, the code generated by moc will call qRegisterMetaType for you if moc can determine that the type may be registered as a. +50. 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 (. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. [virtual] QLocalSocket:: ~QLocalSocket Destroys the socket, closing the connection if necessary. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. You may have to register before you can post: click the register link above to proceed. 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 also makes the type available for queued. 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. To start viewing messages, select the forum that you want to visit from the selection below. . @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). So you can call it from your constructor. 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. You can also use QMetaEnum::fromType() to get the QMetaEnum. 1. To use the type T in QVariant, using Q_DECLARE_METATYPE() is sufficient. It is a static method, it does not (cannot) change x2. Yes, templated types can be used in Qt signal/slots. statement to the header file containing. JulienMaille @kshegunov last edited by JulienMaille . This function was introduced in Qt 4. 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. the type name must be specified without the class, as in. Sorted by: 2. Avoid having to qRegisterMetaType (pointer. Any class or struct that has a public constructor, a public copy constructor, and a public destructor can be registered. 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. See also state() and Creating Custom Qt Types. The class is used to send arguments over D-Bus to remote applications and to receive them back. 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. Additional types can be registered using qRegisterMetaType() or by calling registerType(). 9k 9 34 52. // copiable, C++98 brace-initializable, etc. 1 Answer. To start viewing messages, select the forum that you want to visit from the selection below. Any class or struct that has a public constructor, a public copy constructor, and a public destructor can be registered. 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. However, I cannot figure out how to verify that the included parameter is FACE_UP or FACE_DOWN. Add qRegisterMetaType and qDBusRegisterMetaType calls to enable the framework to work with the custom type. 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. "Custom types used by properties need to be registered using the Q_DECLARE_METATYPE() macro so that their values can be stored in QVariant objects. You can use Q_DECLARE_METATYPE(Widget*) but it is not needed as of Qt. QtCore. Q_DECLARE_METATYPE与qRegisterMetaType学习. 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. To start viewing messages, select the forum that you want to visit from the selection below. hi, I always after application running, receive debug text of: QObject::connect: Cannot queue arguments of type 'MyStruct'. By convention, these files are given a . . I simplified the code quite a bit and the problem went away. [edit] forgot to mention that you also have to use a worker object. The third without Q_DECLARE_METATYPE. From the docs: int qRegisterMetaType ( const char * typeName ) Registers the type name typeName to the type T. Qt is throwing an exception because it doesn't know how to store the shared_ptr onto a QDataStream. enum Qt:: ContextMenuPolicyQObject has neither a copy constructor nor an assignment operator. 14. QMetaType::type () is a bit slower, but compilation succeeds if a type is not registered. Any idea what I'm missing please? BTW, no problem at all using Schedule in QMetaProperty or QVariant. It looks like one can register a type more than once, specifying different typenames, i. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. See also. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. This worked very well. I read on documentation that Q_DECLARE_METATYPE makes available type to QVariant, for example (I got it from documentation): @ struct MyStruct { int i;. To start viewing messages, select the forum that you want to visit from the selection below. qRegisterMetaType vs. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. 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. h in the translation unit where you have that line. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. Q_DECLARE_METATYPE on the other hand is (as far as I know) preprocessor bound. If you only want to store pointer to Foo with the metatype system, then use qRegisterMetaType<Foo *> ();. Constantin. @Q_DECLARE_METATYPE (std::unique_ptr<Thing>);@. Adding a Q_DECLARE_METATYPE () makes the type known to all template based functions, including QVariant. In general, you can only export two kinds of C++ types to QML: QObject-derived classes and some build-in value types, see this documentation page.