Note that if you intend to use the type in queued signal and slot connections or in QObject 's property system, you also have to call qRegisterMetaType () since the names are resolved at runtime. The Custom Type, Custom Type Sending and Queued Custom Type examples show how to implement a custom type with the features outlined in this document. 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. Obviously then you would not do registerComparator (). c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. 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. in a header file and call @qRegisterMetaType<std::unique_ptr<Thing>> ();@ before your signal and slots are used. However, when attempting to compile QCustomPlot in a project using "QT += 3dinput" in its . Even though we do not intend. qRegisterMetaType vs. 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 (. This is not the case, since the following succeeded: @QMetaType::type("MyClass"); // success@. That. 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. View Profile View Forum Posts View Articles Beginner Join Date Nov 2014 Posts 6 Qt products. You can't with Q_GADGETS. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. Is your Q_DECLARE_METATYPE in a header file or an implementation file? Incidentally, there is a mistake in TreeItem. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. 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. 5 is compiled with GCC 4. Adding a Q_DECLARE_METATYPE () makes the type known to all template based functions, including QVariant. Avoid having to qRegisterMetaType (pointer vs reference), concern about const. Call qRegisterMetaType() to make type available to non-template based functions, such as the queued signal and slot connections. The Rep lica C ompiler (repc) generates QObject header files based on an API definition file. QMetaType registerNormalizedTypedef normalizedTypeName, type: metaType ); return. before saveload operation would happen. This results in access violations when Qt. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. Current the only supported type info is QML_HAS_ATTACHED_PROPERTIES. Q_DECLARE_METATYPE与qRegisterMetaType学习. since it is a runtime registration. There's also no need for that typedef, it only makes the code less readable. So in your case you need to declare. 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. You have to register your class to Qt meta objects system. By convention, these files are given a . I want to use my objects as QVariants and for queued connections. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. h) of the derived class. You may have to register before you can post: click the register link above to proceed. QtCore. Then you should register your object to use it with QML. To start viewing messages, select the forum that you want to visit from the selection below. Make sure you call it from within a method. Q_DECLARE_METATYPE (T) requires the type T to be default-constructable, copiable and destructable. Does your code ever call qRegisterMetatype() or use Q_DECLARE_METATYPE()? 10th November 2014, 06:23 #3. 3 Answers Sorted by: 13 "qRegisterMetaType" is a function. Now, that Q_DECLARE_METATYPE enables the type for Qt template classes and QVariant. Please note that I do not use Q_DECLARE_METATYPE on purpose because I don't actually need its features (QVariant expansion) right now. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. 4 which does not support all C++11 features. It is meant to be put in a header where the given type is declared. The third without Q_DECLARE_METATYPE. Qt has to stay free or it will die. Without this reference, it compiles just fine. Email This BlogThis! Share to Twitter Share to Facebook Share to Pinterest. "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. 0. Declare new types with Q_DECLARE_METATYPE () to make them available to QVariant and other template-based functions. The class is used as a helper to marshall types in QVariant and in queued. 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. I placed Q_DECLARE_METATYPE (DataPoint) after the class definition. To make the custom type generally usable with the signals and slots mechanism, we need to perform some extra work. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. Inheritance diagram of PySide6. The QMetaType class manages named types in the meta-object system. Detailed Description. Then the TYPE ID is saved in local static vairable metatype_id. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. It is a static method, it does not (cannot) change x2. Q_DECLARE_METATYPE. @user6556709 I've added both of those, and it does compile now, but the string is just being default initialized to "" when I call value<T>() and there's a red line under Q_DECLARE_METATYPE that says no instance of overloaded function "qRegisterMetaType" matches the argument list, argument types are: (const char [12],. The code compiles and runs ok. 3. 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(). 1. Additionally Qt5 always refers to Q_DECLARE_METATYPE, saying that qRegisterMetaType is only when you want to. The logical equivalent of a const T &r (reference to const T) is a const T * const p (const pointer to const T). 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. 1）引入头文件：#include<QMetaType>. Qt is throwing an exception because it doesn't know how to store the shared_ptr onto a QDataStream. hi, I always after application running, receive debug text of: QObject::connect: Cannot queue arguments of type 'MyStruct'. I guess it's the qRegisterMetaType () call itself that's missing. I also don't want to use qRegisterMetaType, since it is run-time bound. Situation. Make your own typedef and do the Q_DECLARE_METATYPE and qRegisterMetatype. After googling this, I found this correspondence, which was only available through a third party archival site as google. cpp. Enumerations that are declared with Q_ENUM have their QMetaEnum registered in the enclosing QMetaObject. Q_DECLARE_METATYPE, as pointed out by @SingerOfTheFall, would register template based type into QVariant (so it can be retrieved using qvariant_cast<T>()). Otherwise your signals and slots connected used the old mechanism (with macros SIGNAL and SLOT) that require queueing of the parameters won't know how to do so. See also state() and Creating Custom Qt Types. The struct is declared in my worker class, which is inside a namespace. There's also no need for that typedef, it only makes the code less readable. Then you should register your object to use it with QML. ) I have defined MyStruct in an accessible header file: myheader. Note that if you intend to use the type in queued signal and slot connections or in QObject's property system, you also have to call qRegisterMetaType() since the names are resolved at runtime. This replaces the now-deprecated Q_ENUMS and will automatically register the metatype. QList of Custom Objects. Here you can see that the macro expands to nothing. Note that you are technically lying to the meta type system. Q_DECLARE_METATYPE(TYPEDEF) Q_DECLARE_METATYPE(TYPEDEF) mainwindow. 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. 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. I read on documentation that Q_DECLARE_METATYPE makes available type to QVariant, for example (I got it from documentation): @ struct MyStruct { int i;. Q_DECLARE_METATYPE(MyClass*); That's how Qt handles it with QObject and QWidget. Jul 9, 2017 at 21:51. Quote: bool QVariant::operator==(const QVariant & v) const. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. I store them in QVariant :. struct StandardData { int EmpId; QString Name; }; Q_DECLARE_METATYPE (StandardData) Additionally, you might need to call qRegisterMetaType. 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. If the type was not declared with Q_DECLARE_METATYPE (), compilation will fail. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. Q_DECLARE_METATYPE. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries that are used. Similarly you can create a mutable view of type QAssociativeIterable on any container registered with Q_DECLARE_ASSOCIATIVE_CONTAINER_METATYPE(). View Profile View Forum Posts View Articles Beginner Join Date Nov 2014 Posts 6 Qt products. so that was all, but remember to use Q_DECLARE_METATYPE, qRegisterMetaType macros for registering your custom type with Qt meta object system. Alt. . And once all of them are updated I'd like the Context object to inform QML to update the view. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. 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. 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. But I really would like to know the correct way to solve this problem; one where it is not possible to modify. Share. The reasoning is found in the discussion on Identity vs Value on the Qt Object Model page. 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. rep file extension, short for Replica. In. Our first stop for registrations always is the macro Q_DECLARE_METATYPE. e. 1. But I couldn't register the type because it's a QObject and I don't have access to the implementation to change it. It associates a type name to a type so that it can be created and destructed dynamically at run-time. It associates a type name to a type so that it can be created and destructed dynamically at run-time. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. 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. 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. 8. 该类型必须有公有的 构造、析构、复制构造 函数. hpp and qRegisterMetaType<quint32>("quint32"); in both the Constructors of Class1 and Class2. The ones I am registering for are mostly structs for storing data and just a few simple classes. Sorted by: 5. Q_DECLARE_METATYPE(Pkg) and this does not give compile errors, but in my main. To call qRegisterMetaType (), you still need to use Q_DECLARE_METATYPE (). To achieve this you need Q_DECLARE_METATYPE macro and qRegisterMetaType () function. It associates a type name to a type so that it can be created and destructed dynamically at run-time. 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. There's no compile time error, but when I run. 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. This function is useful to register typedefs so they can be used by QMetaProperty, or in QueuedConnections. QLocalSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). QMetaType Synopsis Functions def __eq__ (b). Compares this QVariant with v and returns true if they are equal;. Returns the used WebSocket protocol. It is still giving the error"QObject::connect: Cannot queue arguments of type 'quint32&' (Make sure 'quint32&' is registered using. The same plugin may be loaded multiple times during the application's lifetime. Registered enumerations are automatically registered also to the Qt meta type system, making them known to QMetaType without the need to use. qRegisterMetaType() docs say: 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. It associates a type name to a type so that it can be created and destructed dynamically at run-time. Reply Quote. Ah, sorry, I didn't noticed that part. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. E. Share Improve this answer Follow answered Jul 23, 2014 at 15:37. cpp. Q_DECLARE_METATYPE. 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。. @Q_DECLARE_METATYPE (std::unique_ptr<Thing>);@. 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. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. 1. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. the type name must be specified without the class, as in. But I really would like to know the correct way to solve this problem; one where it is not possible to modify the template classes. This function returns the Qt meta type id for the type (the same value that is returned from qRegisterMetaType()). 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. QList<T> isn't really a pre-defined variant type (except QList<QVariant>) so it technically resolves to a QMetaType::UserType. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. no I didn't, do I need to put in the file generated by repc or I can put it anywhere ? – Houss_gc. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. 24th July 2010, 09:54 #6. hpp which is included in Class1. // But the split allows to. statement to the header file containing. To make the custom. Q&A for work. 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. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. 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. ) 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. Also, to use type T with the QObject::property () API, qRegisterMetaType () must be. In that case, I think you need to register them. QMetaType::type () is a bit slower, but compilation succeeds if a type is not registered. 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. QMetaType::type () is a bit slower, but compilation succeeds if a type is not registered. QML_DECLARE_TYPE. ompiler (repc) generates header files based on an API definition file. The Q_DECLARE_METATYPE() macro and qRegisterMetaType() function documentation contain more detailed information about their uses and limitations. This may make certain type comparisons fail. What worries me is that. void QLocalSocket:: abort ()The signal "orientationChanged" includes an enum of type "Orientation" to indicate if the card has been turned up or down. 0. One of the overloads is a function template that can be used to create an alias for a type and the form is: qRegisterMetaType<Type> ("alias"); That is, it wants to know the type for which you are declaring something. This function was introduced in Qt 6. 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. Hello, Can someone tell me about how to register a metatype in pyqt5. The QMetaType class manages named types in the meta-object system. 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. D-Bus offers an extensible type system, based on a few primitive types and associations of them. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. Q_DECLARE_METATYPE. 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. Here my test code and example:但是如何传递一个程序员自定义的结构体？ 1）在定义结构体之后，要调用Q_DECLARE_METATYPE，向QT声明这个结构体 2）在main. As a workaround, I'm using QVariantMap instead of std::map. Also you may need to use qRegisterMetaType function. To register VideoMeta you need to call qRegisterMetaType<VideoMeta>(). The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. To start viewing messages, select the forum that you want to visit from the selection below. I read on documentation that Q_DECLARE_METATYPE makes available type to QVariant, for example (I got it from documentation): @ struct MyStruct { int i;. 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. To use the type T in QVariant, using Q_DECLARE_METATYPE() is sufficient. . So my first idea:. First of all you need to declare your custom object for Qt metatype system. . See also. 该类型必须有公有的 构造、析构、复制构造 函数. 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. Macros Detailed Description The QMetaType class manages named types in the meta-object system. Normally, you would only register the pointer form if your class cannot be copied, as in the case of QObject and derivatives, but. 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. But at run time, I got below error:1 Answer. Declare new types with Q_DECLARE_METATYPE () to make them available. " Currently I have no UI implemented (yet!). This macro is used to specialise the template class QMetaTypeId with typename TYPE, in which, a static member function qt_metatype_id () is defined. In the example's Message class, a static method is included to do this. To use the type T in queued signal and slot connections, qRegisterMetaType () must be called before the first connection is established. 23k 10 10 gold. Assuming base and derived are Q_GADGETs you want to get a static member. 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. 2. You should use qmlRegisterType function for that. What is(are) the good place(s) to put the qRegisterMetaType call? I obviously don't want any expllicit. qRegisterMetaType 必须使用该函数的两种情况. Re: How to use Q_DECLARE_METATYPE. So I tried declaring the following at end of my worker thread class Q_DECLARE_METATYPE(cv::Mat);. 4 and it seems to work. Some structure need to be registered to be queued in asynchronous signals using qRegisterMetaType<T>(name), such as signal which passes QVector<int>. To start viewing messages, select the forum that you want to visit from the selection below. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. Enumerations that are declared with Q_ENUM have their QMetaEnum registered in the enclosing QMetaObject. append (QVariant::fromValue (l)); } return list; } The metatype system declaration and registration you have. genC last edited by . QMetaType. 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. Using the Q_DECLARE_METATYPE () macro 2. 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. QtCore. g. Detailed Description. 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. namespace CCS { Q_DECL_EXPORT Q_NAMESPACE. [override virtual] bool QAbstractSocket:: waitForBytesWritten (int msecs = 30000) Reimplements: QIODevice::waitForBytesWritten(int. e. template <typename T> struct QMetaTypeId<Container<T>>. 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. This function was introduced in Qt 6. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. 2. Actually, they are declared, but in a private section with the macro Q_DISABLE_COPY(). 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 (). canConvert<x> (); } and. Of course it's a bug and an odd mistake that Q_DECLARE_METATYPE(QList<QSslError>) is in qsslsocket. F. 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. After googling this, I found this correspondence, which was only available through a third party archival site as google. e. io Please note that I do not use Q_DECLARE_METATYPE on purpose because I don't actually need its features (QVariant expansion) right now. For that, I want to declare a. 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. @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. To start viewing messages, select the forum that you want to visit from the selection below. There is no way to add support for more of these value types like std::string (*). To start viewing messages, select the forum that you want to visit from the selection below. qRegisterMetaType<signed long long>() - do nothing. i. Read and abide by the Qt Code of Conduct. 3. It does not say anything about registering the type. Sorted by: 1. Also Q_DECLARE_METATYPE does not register a type, but declares it. Is your Q_DECLARE_METATYPE in a header file or an implementation file? Incidentally, there is a mistake in TreeItem. When I emit a signal, then I get next error to the output stream:. @Q_DECLARE_METATYPE (std::unique_ptr<Thing>);@. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. This is by design. Q_DECLARE_METATYPE on the other hand is (as far as I know) preprocessor bound. 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. There's no need to call qRegisterMetaType that many times, once is enough. QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_REGISTER_METATYPE() and qRegisterMetaType(). 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. 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. You may have to register before you can post: click the register link above to proceed. 3 to Qt4. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. The QMetaType class manages named types in the meta-object system. 4 which does not support all C++11 features. Read and abide by the Qt Code of Conduct. The documenation of this macro gives. You had to use QMetaType::registerComparators () and the other static register functions in QMetaType to actually make use of that functionality, though. 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. You may have to register before you can post: click the register link above to proceed. That always worked in Qt4, but in Qt5 I get the following error: @error: specializing member ‘::qRegisterMetaType<Subclass>’ requires ‘template<>’ syntax@. It associates a type name to a type so that it can be created and destructed dynamically at run-time. I also added qRegisterMetaType<DataPoint> () to the initialisation method of my main. Q_DECLARE_METATYPE(TYPEDEF) Q_DECLARE_METATYPE(TYPEDEF) mainwindow. QObject can't be copied and all its descendants can't be copied also. This won't work because you can't use qMetaTypeId<> () before Q_DECLARE_METATYPE<>. Yes, templated types can be used in Qt signal/slots. So, whatever Q_DECLARE_METATYPE is doing cannot be done by writing a function call. This has been changed, and isNull () now only returns true if the QVariant is empty or contains a nullptr. ) QObject::connect: Cannot queue arguments of type 'QVector<int>'. qRegisterMetaType is also called in the class constructor. e. As a workaround, I'm using QVariantMap instead of std::map. Now you have a valid QObject. From the docs: int qRegisterMetaType ( const char * typeName ) Registers the type name typeName to the type T. 0. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. qRegisterMetaType<FileNodePointer> ("FileNodePointer"); should be called once (in main, constructor etc. Here’s the list of what changed: QVariant used to forward isNull () calls to its contained type – but only for a limited set of Qt’s own types. 9k 9 34 52. Q_DECLARE_METATYPE与qRegisterMetaType学习. However, as you need the type to be. If you are using queued connections, you need to register std::string as meta type. So, if you had a custom type FooType, you'd put the Q_DECLARE_METATYPE directly after the declaration, and in. This won't work because you can't use qMetaTypeId<> () before Q_DECLARE_METATYPE<>. 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. It associates a type name to a type so that it can be created and destructed dynamically at run-time. There's no compile time error, but when I run. I'm using Qt 5. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. Franzk 26 May 2011, 06:59. Returns the metatype of the parameter at the given index. 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. Call qRegisterMetaType () to make type available to non-template based. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. It was also no big issue to call qRegisterMetaType () automatically. 2. So I don't stream the pointer itself just copy the properties and set them to a new created pointer object. It seems that for a metatype that is a QList<MyClass::MyEnum> I must. Qt. Original Question. Do do you register the meta type with the call qRegisterMetaType("your custom meta type")? 1 Reply Last reply Reply Quote 0. If you need the functionality provided by Q_DECLARE_METATYPE, you will have to use it. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. 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.