The QMetaType class manages named types in the meta-object system. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. type() typeName() PySide6. nyaruko. A. As the docs state: Declare new types with Q_DECLARE_METATYPE () to make them available to QVariant and other template-based functions. 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. Q_DECLARE_METATYPE. 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 have an application that requires use of both Qt 3D and the QCustomPlot library. qRegisterMetaType vs. From the docs: int qRegisterMetaType ( const char * typeName ) Registers the type name typeName to the type T. Call qRegisterMetaType() to register the data type before you establish the connection. 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. You may have to register before you can post: click the register link above to proceed. 2、在类型定义完成后，加入声明：Q_DECLARE_METATYPE (MyDataType); 3、在main ()函数中. 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. A separate point for your own benefit. 0. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. I read a bit and it seems that Q_DECLARE_SMART_POINTER_METATYPE is supposed to allow this to work. ", which suggests it is only for classes and structs. QtCore. // But the split allows to. Using Qt 3D with QCustomPlot. 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. Read and abide by the Qt Code of Conduct. That class receives a list of variants (wrapping various data) and converts those variants into a binary stream using QDataStream >. It looks like one can register a type more than once, specifying different typenames, i. This is by design. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. Q_DECLARE_METATYPE(Pkg) and this does not give compile errors, but in my main. Thus you need to use the runtime check QMetaType::type (). 2. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. This may make certain type comparisons fail. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. It is more or less explained in the manual for int qRegisterMetaType (const char *typeName) This function requires that T is a fully defined type at the point where the function is called. namespace CCS { Q_DECL_EXPORT Q_NAMESPACE. Qt is throwing an exception because it doesn't know how to store the shared_ptr onto a QDataStream. 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. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. With Q_DECLARE_METATYPE and without qRegisterMetaType: No warning, slot is called With Q_DECLARE_METATYPE and with qRegisterMetaType: No warning, slot is called. In Qt, you can declare a variable in two ways: 1. void QAbstractSocket:: abort ()Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. e. One of these plugins uses Q_DECLARE_METATYPE on some types that need to be stored in a QVariant. As a workaround, I'm using QVariantMap instead of std::map. QtCore. This article will. From the QVariant::value documentation: If the QVariant contains a pointer to a type derived from QObject then T may be any QObject type. :) QApplication is the root QObject of the program and its full initialization is required before anything can practically be done with anything else. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. See also isRegistered () and Q_DECLARE_METATYPE (). I tested your code on Qt 5. pro file, several errors appear referencing the QMouseEvent and QWheelEvent classes. Any class or struct that has a public default constructor, a public copy. It seems that for a metatype that is a QList<MyClass::MyEnum> I must. Re: Q_DECLARE_METATYPE problem. Registers the type name . Thanks for the suggestion. Call qRegisterMetaType() to make type available to non-template based functions, such as the queued signal and slot connections. 12. Is your Q_DECLARE_METATYPE in a header file or an implementation file? Incidentally, there is a mistake in TreeItem. As said in int qRegisterMetaType () documentation: To use the type T in QVariant, using Q_DECLARE_METATYPE () is sufficient. 2）添加声明：利用宏 Q_DECLARE_METATYPE. 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. qRegisterMetaType() requires also a Q_DECLARE_METATYPE() – dtech. Mixing doesn't work but if you always use one or the other it works. 0 and have problems registering my own class as a QMetaType. Using the Q_DECLARE_METATYPE () macro 2. So in your case you need to declare. 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. Add qRegisterMetaType and qDBusRegisterMetaType calls to enable the framework to work with the custom type. 如果非QMetaType内置类型要. no unexpected garbage. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. Follow answered Jun 5, 2009 at 15:14. J 1 Reply Last reply Reply Quote 0. See also Thread Support in Qt, QObject::connect(), qRegisterMetaType(), and Q_DECLARE_METATYPE(). until today. 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. PySide6. Learn more about Teams I can't figure out a way to automatically declare a meta type, i. The ones I am registering for are mostly structs for storing data and just a few simple classes. Q_DECLARE_METATYPE, as pointed out by @SingerOfTheFall, would register template based type into QVariant (so it can be retrieved using qvariant_cast<T>()). uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. See also. I think you need to add an explicit export/import directive to the QT_NAMESPACE macro. 1. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. . Don't use Q_DECLARE_METATYPE and qRegisterMetaType for your QObject enum. Declare new types with Q_DECLARE_METATYPE () to make them available. Custom Type Qlist and Scope. Any class or struct that has a public default constructor, a public copy constructor, and a. {. QMetaType Synopsis Functions def __eq__ (b). 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 () <<. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries that are used. So you can call it from your constructor. ) I have defined MyStruct in an accessible header file: myheader. qRegisterMetaType vs. But at run time, I got below error:1 Answer. Q_DECLARE_METATYPE (T) requires the type T to be default-constructable, copiable and destructable. Original Question. I have a problem with a class that exchanges data using TCP/IP socket. Type is not registered, please use the Q_DECLARE_METATYPE macro to make it known to Qt's meta-object system. Q_DECLARE_METATYPE only registers a type in meta type system. See also. @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. Consider the specific case of qRegisterMetaType. One of these plugins uses Q_DECLARE_METATYPE on some types that need to be stored in a QVariant. Note that you are technically lying to the meta type system. Inheritance diagram of PySide6. 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. 1 Answer. 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. I need to call the Q_DECLARE_METATYPE() to pass the smart pointer. QList<AnotherObject*> has of course been registered with Q_DECLARE_METATYPE and qRegisterMetaType(). This has been changed, and isNull () now only returns true if the QVariant is empty or contains a nullptr. In fact, all Qt classes derived from QObject (direct or indirect) use this macro to declare their copy constructor and assignment operator to be private. Basically, I created a library containing a type: struct MyCustomType {. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. Q&A for work. 11. I thought there was a bug with QMetaType or Q_DECLARE_METATYPE. QMetaType::type () is a bit slower, but compilation succeeds if a type is not registered. You may have to register before you can post: click the register link above to proceed. . h instead ofQVariant x2; x2. From the docs: int qRegisterMetaType ( const char * typeName ) Registers the type name typeName to the type T. In my own code, I use Q_DECLARE_METATYPE for classes I want to store. nyaruko. You may have to register before you can post: click the register link above to proceed. qRegisterMetaType usage. The fix is probably to include qsslsocket. View Profile View Forum Posts View Articles Beginner Join Date Nov 2014 Posts 6 Qt products. I only care about runtime instantiation. . Q_DECLARE_METATYPE on the other hand is (as far as I know) preprocessor bound. First of all, you always need to declare your meta type: Q_DECLARE_METATYPE (foo::MyClass) It works at compile time, so there are no limitations on how you refer to your class. qRegisterMetaType () is called to register the TYPE and generate a TYPE ID. So you can call it from your constructor. This fixed the issue. Does your code ever call qRegisterMetatype() or use Q_DECLARE_METATYPE()? 10th November 2014, 05:23 #3. QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). If you only want to store pointer to Foo with the metatype system, then use qRegisterMetaType<Foo *> ();. Note that for enum types, you no not even need to call qRegisterMetaType () in these cases. The file (called a "rep" file) uses a specific (text) syntax to describe the API. 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. e. 2. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. enum Qt:: ContextMenuPolicycall qRegisterMetaType() to register the data type before you call QMetaMethod::invoke(). To use the type T in QVariant, using Q_DECLARE_METATYPE() is sufficient. It associates a type name to a type so that it can be created and destructed dynamically at run-time. [since 6. 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 ;. QObject::connect: Cannot queue arguments of type 'MyStruct'. With Q_DECLARE_METATYPE and without qRegisterMetaType: No warning, slot is called With Q_DECLARE_METATYPE and with qRegisterMetaType: No warning, slot is called. 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. g. 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. See also state () and Creating Custom Qt Types . Now, that Q_DECLARE_METATYPE enables the type for Qt template classes and QVariant. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. 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. g. As a result, if the library connects a D-Bus signal to a slot with a signature "void mySlot (MyType)", it is. Qt5でシグナルの引数としてユーザー定義型を指定する場合は、Q_DECLARE_METATYPEとqRegisterMetaType()を使って方の登録を行う必要がある。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. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. Then the TYPE ID is saved in local static vairable metatype_id. There's no need to call qRegisterMetaType that many times, once is enough. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. Then after some time, we can begin answering them. I have declared all the types with Q_DECLARE_METATYPE, Q_OBJECT and the properties with Q_PROPERTY with the proper getters and setters. When I emit a signal, then I get next error to the output stream:. Returns the internal ID used by QMetaType. QMetaType::type () returns the same ID as qMetaTypeId (), but does a lookup at runtime based on the name of the type. See also Thread Support in Qt, QObject::connect(), qRegisterMetaType(), and Q_DECLARE_METATYPE(). call qRegisterMetaType with the name specified, else reading properties. 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. 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. 5 is compiled with GCC 4. " Yet types like QVariantMap are themself typedefs. However, as you need the type to be. The logical equivalent of a const T &r (reference to const T) is a const T * const p (const pointer to const T). no unexpected garbage. 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 only registers a type in meta type system. 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. Note: This function is thread-safe. It associates a type name to a type so that it can be created and destructed dynamically at run-time. There's no need to call qRegisterMetaType that many times, once is enough. @Wieland Thanks. That would allow you to use. Ah, sorry, I didn't noticed that part. You can also use QMetaEnum::fromType() to get the QMetaEnum. The problem of owner ship of the memory is avoided. Follow. Is your Q_DECLARE_METATYPE in a header file or an implementation file? Incidentally, there is a mistake in TreeItem. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. 2. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. This function was introduced in Qt 6. w/out GUI module you wouldn't have any of those types available). QVariant x2 = QVariant::fromValue( x1); To copy to clipboard, switch view to plain text mode. 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. Q&A for work. I explicitly don't want to update it on every change to one of the quantities, so they don't. Also Q_DECLARE_METATYPE does not register a type, but declares it. Additional types can be registered using qRegisterMetaType() or by calling registerType(). This results in access violations when Qt. To start viewing messages, select the forum that you want to visit from the selection below. [virtual] QLocalSocket:: ~QLocalSocket Destroys the socket, closing the connection if necessary. qRegisterMetaType is also called in the class constructor. I also added qRegisterMetaType<DataPoint> () to the initialisation method of my main. on top of main. 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. I'm confused by this error, as the documentation states (emphasis mine): Returns the meta type id of type T at compile time. Improve this answer. M. 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_REGISTER_METATYPE() and qRegisterMetaType(). 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. Hello Ladies and Gentlemen. template <typename T> struct QMetaTypeId<Container<T>>. It was also no big issue to call qRegisterMetaType () automatically. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. Last updated at 2016-07-08 Posted at 2015-11-16. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries that are used. Detailed Description. In the example's Message class, a static method is included to do this. 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(). Q_DECLARE_METATYPE(MyClass*); That's how Qt handles it with QObject and QWidget. Re: Qt warning of type conversion already registered Originally. The correct syntax is Q_DECLARE_METATYPE (std::string) without the ;. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. Data Type Conversion Between QML and C++. There's no compile time error, but when I run. I am also using some in queued signal and slot connections. container. That's created by this macro. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. Here you can see that the macro expands to nothing. Sorted by: 2. I only care about runtime. Any class or struct that has a public default constructor, a public copy. Make sure you call it from within a method. This worked very well. 3. Now you have a valid QObject. Labels: meta system, Meta type, qt. This version of the function is to register alias types. 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. I my real world application Context holds a large number of physical quantities (masses, forces, velocities,. ), or any other callable, cannot declare a type for use outside of the call site. Read and abide by the Qt Code of Conduct. I have created an qt bugticket hoping the documentation will be extended. QLocalSocket. Any class or struct that has a public default constructor, a public copy constructor, and a public destructor can be registered. ) is supported. Q_DECLARE_METATYPE. Q_DECLARE_METATYPE(TYPEDEF) Q_DECLARE_METATYPE(TYPEDEF) mainwindow. The struct is declared in my worker class, which is inside a namespace. Re: Q_DECLARE_METATYPE vs qRegisterMetaType for non global namespace classes (QTest) The reason for this behavior might be caused by the fact that runtime signal/slot connections are checked by string manipulation - both Q_DECLARE_METATYPE, SIGNAL, SLOT macros and 'moc' are (among other things) converting type-names to text and pass it along. Any class or struct that has a public constructor, a public copy constructor, and a public destructor can be registered. I am also using some in queued signal and slot connections. 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",. so that was all, but remember to use Q_DECLARE_METATYPE, qRegisterMetaType macros for registering your custom type with Qt meta object system. The docs only talk about class or struct with public default constructor, copy constructor and. To use the type T in queued signal and slot connections,. I have a few instances of QVector<MyClass> which I want them to be exposed to QScriptEngine. qRegisterMetaType vs. 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. The object it returns should also be a member of the factory class. no unexpected garbage. That's probably there, as qRegisterMetaType () wouldn't compile otherwise. This allows us to use the Enum as a custom-type of a QVariant, to pass it between QML and Qt, to use it in synchronous signal-slot connections, and to print the symbolic enums (instead of a magic number) with qDebug(). QList<T> isn't really a pre-defined variant type (except QList<QVariant>) so it technically resolves to a QMetaType::UserType. In the header, after the class declaration, outside the namespace, I've included. So using a QString as the type of a Q_PROPERTY only works because it has special built-in support in the QML engine. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. Read and abide by the Qt Code of Conduct. 1 Answer. e. For this, a function call (evaluated during runtime) needs to be made, and qRegisterMetatype is the tool for this: qRegisterMetaType<Area>("Area");@julio. When using signals and slots with multiple threads, see Signals and Slots Across Threads. It does not say anything about registering the type. At the point where I want to read the list, I only care about (and know) the fact that the list contains pointers to objects, which have been derived. 0. In short, I get following error: QObject::connect: Cannot queue arguments of type 'cv::Mat' (Make sure 'cv::Mat' is registered using qRegisterMetaType (). Since Qt 5. . 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. 1. Qt Base (Core, Gui, Widgets, Network,. Jun 13, 2021 at 19:37. You may have to register before you can post: click the register link above to proceed. There's no such thing as a "const reference" because references are always const -- you can't reseat them. The default access for a class is private, so that Container* data();. : Q_DECLARE_METATYPE(MyClass*); That's how Qt handles it with QObject and QWidget. Using the following required me to use Q_DECLARE_METATYPE. 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. Detailed Description. Step 1 (mark for MOC), build some QObjects That pattern uses Q_PROPERTY and Q_OBJECT and the MoC tool. 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. [virtual] QLocalSocket:: ~QLocalSocket Destroys the socket, closing the connection if necessary. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. 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. [override virtual] bool QLocalSocket:: waitForBytesWritten (int msecs = 30000) Reimplements:. 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. [since 6. I store them in QVariant :. Note: it's also safe to call qRegisterMetaType () multiple times. G. Yes, templated types can be used in Qt signal/slots. Also you may need to use qRegisterMetaType function. your custom type definition. Normally, you would only register the pointer form if your class cannot be copied, as in the case of QObject and derivatives, but. Use Q_DECLARE_OPAQUE_POINTER () to be able to register pointers to forward. The same plugin may be loaded multiple times during the application's lifetime. There's also no need for that typedef, it only makes the code less readable. Learn more about Teams Declaring a meta type. The QML engine provides built-in support for a. Macros Detailed Description The QMetaType class manages named types in the meta-object system. 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。. Sorted by: 3. Q_DECLARE_METATYPE(Pkg) and this does not give compile errors, but in my main. I want to use drag-and-drop to drag a QTreeWidgetItem that has std::shared_ptr user data. Declare new types with Q_DECLARE_METATYPE () to make them available. I meet a qt metatype issue. Share Improve this answerWe will still need to register it with the meta-object system at run-time by calling the qRegisterMetaType() template function before we make any signal-slot connections that use this type. Q_GADGET makes a class member, staticMetaObject, available. Franzk 26 May 2011, 06:59. 4] QString QWebSocket:: subprotocol const. You can use Q_DECLARE_METATYPE(Widget*) but it is not needed as of Qt. The QMetaType class manages named types in the meta-object system. 如果非QMetaType内置类型要. Any class or struct that has a public default constructor, a public copy. This also makes the type available for queued. Q_DECLARE_METATYPE. Although I'm. 该类型必须有公有的 构造、析构、复制构造 函数. See also state() and Creating Custom Qt Types. Duplicate Question(s):Q_DECLARATIVE_METATYPE in and out; Using EventExport vs. 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 Problem: I want to create an object instance at runtime using QMetaType by the type name. qRegisterMetaType vs. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. 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. There's no compile time error, but when I run. 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. The ones I am registering for are mostly structs for storing data and just a few simple classes. Note that if you intend to use the type in queued signal and slot connections or in QObject 's property system, you also have to call qRegisterMetaType () since the names are resolved at runtime. QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_REGISTER_METATYPE() and qRegisterMetaType(). Obviously then you would not do registerComparator (). Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). [edit] forgot to mention that you also have to use a worker object. Similarly you can create a mutable view of type QAssociativeIterable on any container registered with Q_DECLARE_ASSOCIATIVE_CONTAINER_METATYPE(). This function was introduced in Qt 4. 14. 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. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. QtNetwork. qRegisterMetaType vs. h" class Context : public QObject { Q_OBJECT Q_PROPERTY (MyGadget* gadget READ gadget CONSTANT) public: explicit Context () : QObject {nullptr} { } MyGadget* gadget () { return &_gadget; } private. Per Qt documentation: To use the type T in QVariant, using Q_DECLARE_METATYPE () is sufficient. The. Obviously then you would not do registerComparator (). To enable using the type in queued signals and such, there also needs to be a corresponding call: qRegisterMetaType<foo::FooState>(); Question. qt. since it is a runtime registration. Now, that Q_DECLARE_METATYPE enables the type for Qt template classes and QVariant. Qt has to stay free or it will die. Type is not registered, please use the Q_DECLARE_METATYPE macro to make it known to Qt's meta-object system. I placed Q_DECLARE_METATYPE (DataPoint) after the class definition. 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. Step 1 (mark for MOC), build some QObjects That pattern uses Q_PROPERTY and Q_OBJECT and the MoC tool. complains that the metatype isn't registered. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). qRegisterMetaType vs. There's no need to call qRegisterMetaType that many times, once is enough. Here you can see that the macro expands to nothing.