QObject::connect: Cannot queue arguments of type 'object' (Make sure 'object' is registered using qRegisterMetaType(). 如果要使用单个全局类来访问QML或从QML访问. template <typename T> struct QMetaTypeId<Container<T>>. std::shared_ptr does not let you assign a plain pointer to it directly. Specifically, the function have to be called before using the struct in a queued signal/slot connection or. 31. In QML, the meta-type system is the only way that QML engine can access C++ structures from a QML environment. Note that this only works for QObject subclasses which use the Q_OBJECT macro. Detailed Description. Warning. When these files are processed by repc, repc generates both Source and Replica header files. 独自の QTcpServer を構築する. It also reflects the size of the paging file at that time. adam-iris added a commit that referenced this issue Oct 10, 2017. (Make sure 'QTextCursor' is registered using qRegisterMetaType (). ) I have Googled for eons trying to figure out a way how to use the qRegisterMetaType() in PySide, to no avail. However Q_DECLARE_METATYPE () is a bit more complicated. 步骤： (以自定义MyDataType类型为例）. e. self. . 如果要使自定义类型或其他非QMetaType内置类型在QVaiant中使用，必须使用该宏。. QModbusDataUnit can be used for read and write operations. The physical memory sizes returned include the memory from all nodes. beginGroup("references/"); QStringList keys = settings. I got confused by the documentation and I declared my typedef on line 10 and then I put qRegisterMetaType<AvailablePorts>("AvailablePorts") on line 11. 2 @Alfredocubitos would it be possible to share an example of the threaded websocket. In C++ if you wan't to use some type in queued connection type you should call qRegisterMetaType<MyType> ("MyType"). MainWindow win; win. {. In C++ if you wan't to use some type in queued connection type you should call qRegisterMetaType<MyType> ("MyType"). QVariant’s operator== now uses QMetaType::equals for the comparison. Now, this simple class holds small samples of. 步骤： (以自定义MyDataType类型为例）. QtWidgets import * Er. It's a bit tricky thing. // to be declared somewhere Q_DECLARE_METATYPE(std::string); // to be invoked at the beginning of program qRegisterMetaType<std::string>(); Without type registration Qt doesn't know how to do a copy and provides a warning in logs. The compound types are then created by association of one or more of the primitive types in arrays, dictionaries or structures. This function was introduced in Qt 5. (Make sure 'uint64' is registered using. 04 with anaconda distribution of python 3. ) ^C[rviz-2] killing on exit [laserMapping-1] killing on exit Hello guys, i have the following message when i run the launch file. If you ever wondered what does Q_DECLARE_META_TYPE or qRegisterMetaType do and when to use (or not to use) them, read on. Returns a list of child objects. For example if you have a customwidgetscript. Debugging signals and slots connections. If the signal is being emitted, I get this error: @. You should use qmlRegisterType function for that. The Qt Meta-Object System in Qt is responsible for the signals and slots inter-object communication mechanism, runtime type information, and the Qt property system. QAbstractSocket is the base class for QTcpSocket and QUdpSocket and contains all common functionality of these two classes. registerType () determines which register is used for the operations. The QML engine provides built-in support for a. QObject::connect: Cannot queue arguments of type 'QVector<int>'. ) The image I am trying to pass is a cv::Mat which I converted to a QImage which I afterwards converted to a QString. 0, so Q_ENUM is my variant. data = new double [channel_count]; std::copy (input_data, input_data+channel_count, data); in the dtor of this class the data ptr is deleted. QMetaMethod::Access QMetaMethod:: access const. Asking for help, clarification, or responding to other answers. For a signal-functor connection without a context object, it is the only way to selectively disconnect that connection. on top of main. (Make sure 'QVector<int>' is registered using qRegisterMetaType(). The application may need to relay this clicking event to other applications. 10, enumerations are directly supported in QML. C++ (Cpp) qmlRegisterUncreatableMetaObject - 2 examples found. I am trying to learn Qt and I am attempting to do so by making a little titres game. Its probably something about Qt, but how can i fix it ?Member Function Documentation [explicit] QQmlEngine:: QQmlEngine (QObject *parent = nullptr) Create a new QQmlEngine with the given parent. • Posting events with QApplication::postEvent(), or using queued signal/slot connections, are both safe mechanisms for communicating across threads but require the receiving thread. I'm using Qt 5. Also I get warnings: QObject::connect: Cannot queue arguments of type 'QTextBlock' (Make sure 'QTextBlock' is registered using qRegisterMetaType (). If you use queued connections, you'll need to call qRegisterMetaType() too. If such a connection is made, and a signal triggered, the runtime warning will be shown: QObject::connect: Cannot queue arguments of type 'T' (Make sure 'T' is registered using qRegisterMetaType (). @SGaist Yes, I am using it with QVariant, mostly with QSettings to save and retrieve data easily by overriding QDataStream operators. template<class T> QMetaObject::Connection connect_from_pointer ( const QSharedPointer<T>& sender,. Note that if you intend to use the type in queued. by using qRegisterMetaType(). runtime barfs if the signature for test in both headers and . 这两个东西真难理清，不妨看看源码吧。. What is the expected behavior. karensantana. The Qt GUI module contains classes for 2D graphics, imaging, fonts, and advanced typography. ) @. @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). You have to register your custom type for queued signals because by registering it, Qt can make a copy of it in its event loop (which certainly uses QVariant) and pass it as argument later (when the original passed value is long since out. First of all, shared_ptr needs an (external, in general) reference counter to be allocated. @RIJIK "very unlikely" doesn't mean never ever. This member is allocated and filled with data from a qt slot like so: int channel_count =. ) QObject: Cannot create children for a parent that is in a different thread. You can use Qt's typedef for unsigned char: quint8 and you don't need to register it. py that implements a customwidget class it would look something like: from customwidgetscript import customwidget. 二者的联系： QMetaTypeId<TYPE>的类中的成员包含对qRegisterMetaType的调用. No, everything is in separated folders. qRegisterMetaType<QSqlDatabase>("QSqlDatabase"); Just changing the signal to this form: void dbConnected(QSqlDatabase *db); And, in the slot side I'll use something like this: void onDBConnected(QSqlDatabase * const db); I'm concerned with the usage of db (as in the beginning I've made the reference const), so I make it const here. It contains a bin folder with the exe file and batch launchers, an include folder with the headers, a source folder with the source files and the moc file (cpp). QObject::connect: Cannot queue arguments of type 'QVector<int>' (Make sure 'QVector<int>' is registered using qRegisterMetaType(). QObject. Fixes #46, the logging handler was trying to update a GUI element dir…. Make sure you call it from within a method. E. Any class or struct that has a public default constructor, a public copy constructor , and a. That's probably there, as qRegisterMetaType () wouldn't compile otherwise. ) QObject::connect: Cannot queue arguments of type 'QVector' (Make sure 'QVector' is registered using qRegisterMetaType(). h file. I realize that this actually works when more than one signal of different types is sent, e. On this windows 7 machine, I have installed Python 3. org is deprecated as of August the 11th, 2023. To avoid never ending notification loops you can temporarily block signals. websocket. pro file: CONFIG += qmltypes. Use Q_DECLARE_METATYPE (std::string) in one of your headers. @reddy9pp said in QObject::connect: Cannot queue arguments of type 'std::string' (Make sure 'std::string' is registered using qRegisterMetaType(). Any class or struct that has a public default constructor, a public copy constructor and a public destructor can be registered in QMetaType. QDBusArgument is the central class in the Qt D-Bus type system, providing functions to marshall and demarshall the primitive types. If I register QVector I can't dissconnect this signal and the signal is emited. Thanks for replying! I'm using Qt 5. Hi, you can try using a more robust flavor of connect() by adding an argument after the lambda, like this: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. See also. ) QObject::connect: Cannot queue arguments of. Detailed Description#. The. qmlRegisterUncreatableType# qmlRegisterUncreatableType (pytype: type, uri: str, versionMajor. If I save the image to disk in the DB thread just after emitting the signal, it is good. To register VideoMeta you need to call qRegisterMetaType<VideoMeta>(). layoutAboutToBeChanged. 12. ) What I have done is, declare in the main the qRegisterMetatype but it still complaining. d. You can call this function in a subclass of QAbstractSocket to change the return value of the localPort () function after a connection has been established. I read on documentation that Q_DECLARE_METATYPE makes available type to QVariant, for example (I got it from documentation): @ struct MyStruct { int i;. The Qt doc on qRegisterMetaType explicitly says : T must be declared with Q_DECLARE_METATYPE (). The habit of passing shared_ptr by ref should not be followed in lambdas. Although I have not made clear the specific meaning, at least it can work well. 2. Inheritance diagram of PySide6. ) but does not allow the transmission of data between threads, for this case it must be registered using qRegisterMetaType<MyClass::ErrorCode>("ErrorCode"): main. Where are you getting this from? qRegisterMetaType is not a member function of QSettings or any other class. Undeclared QMetaObject::SuperData. ) QObject::connect: Cannot queue arguments of type 'QVector<int>'. If I register QVector I can't dissconnect this signal and the signal is emited. Here how connect looks in main constructor: connect (w1, SIGNAL (sentInt (int)), this, SLOT (receiveInt (int))); Such simple app works, but if i change parameters from int to "signed long long" it will give message during runtime and signal won't be emitted: QObject::connect: Cannot queue arguments of type 'signed long long'. [quote author="Andre" date="1306394817"]In that case, I think you need to register them. The QObjectList class is defined in the <QObject> header file as the following: typedefQList<QObject*>QObjectList; The first child added is the first object in the list and the last child added is the last object in the list, i. com to ask a new question. You can try it:This function registers the Python type in the QML system with the name qmlName, in the library imported from uri having the version number composed from versionMajor and versionMinor. runBtn = QtWidgets. ) What I have done is, declare in the main the qRegisterMetatype but it still complaining. 4. As the docs state: Declare new types with Q_DECLARE_METATYPE () to make them available to QVariant and other template-based functions. qRegisterMetaType<Subclass> ("Subclass") also doesn't work. Qt also has a macro Q_DECLARE_METATYPE, which is expanded and specialized in the class QMetaTypeId. Data Type Conversion Between QML and C++. Bachir. This class can tell the outside world that its state has changed by emitting a signal, valueChanged(), and it has a slot which other objects can send signals to. Convert this variant to type QMetaType::UnknownType and free up any. ) The form here shows the exactly same problem but I can't use signal and slot as. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. This implies that you can create bindings that use this property as a dependency or install QPropertyObserver objects on this property. Consider for example the following (hypothetical) code:The Listmodel should be modified by an AMQP-Eventqueue. 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. See QMetaType docs for more information. Variant 2: use std::invoke inside a lambda, which is passed to QMetaObject::invoke. The following code allocates and destructs an instance of MyClass: The Q_DECLARE_METATYPE() macro and qRegisterMetaType() function documentation contain more detailed information about their uses and limitations. 2 Answers Sorted by: 3 You do not need to call qRegisterMetaType () to use a type with QVariant. Then the TYPE ID is saved in local static vairable metatype_id. 0. OTOH, passing it by value in lambdas too is dangerous and can cause memory leaks. 1、自定MyDataType 类型，在这个类型的顶部包含：#include <QMetaType>. That always worked in Qt4, but in Qt5 I get the following error: @error: specializing member ‘::qRegisterMetaType’ requires ‘template<>’ syntax@ qRegisterMetaType("Subclass") also doesn't workI am using ubuntu 16. 15. Placing logic such as a script or other operations in the handler. You get this because you are creating the QNetworkAccessmanager in the constructor of Citizen, which is being called in the "original" thread. PySide6. QTextCharFormat. 1. It is. #include<QMetaType> typedef QList<int> IntList; qRegisterMetaType<IntList> ("IntList"); error C2909: 'qRegisterMetaType': explicit instantiation of function template requires return type. Edit: from @altaf comments : To clarify, the root of the problem was cause by qRegisterMetaType<Data> ("Data"); in my main. ) summary refs log tree commit diff statsHello! Thanks for the package. The only changes were made to initArgs and appendArgs functions. The following example records all signal emissions for the clicked () signal of a QCheckBox:Step 1 (mark for MOC), build some QObjects That pattern uses Q_PROPERTY and Q_OBJECT and the MoC tool. Data should be passed by pointers through signals and slots, so it should be registered as, something like qRegisterMetaType<*Data> ("pData"); All signals and slots should take the arguments. 根据类型名. There's no compile time error, but when I run. Detailed Description. Appears to the right of the line. 0’ of a module called ‘com. 3k 33 33 silver badges 58 58 bronze badges. This requires the exchanged data to be of a type that is recognizable by the engine. akshatrai91 7 Jan 2021, 06:21. More frustrating is I've found PySide documentation alluding to the use of qRegisterMetaType, but I can't find out where to call it from. First of all you need to declare your custom object for Qt metatype system. The Qt doc on qRegisterMetaType explicitly says : T must be declared with Q_DECLARE_METATYPE (). Make a typedef for QSharedPointer<UserDataType>, and use both Q_DECLARE_METATYPE as well as qRegisterMetaType () to register it for use. To use the type T in queued signal and slot connections, qRegisterMetaType () must be called before the first connection is established. Sets the port on the local side of a connection to port. Finds signal and returns its index; otherwise returns -1. When a new folder is selected I load the thumbnails and. QObject::connect: Cannot queue arguments of type 'QVector<QVector<int> >'. See also Q_DECLARE_METATYPE() and qRegisterMetaType(). I get the following listed in the Application Output pane in QtCreator: QObject::connect: Cannot queue arguments of type 'QQmlChangeSet' (Make sure 'QQmlChangeSet' is registered using qRegisterMetaType (). October 21, 2020 by Fabian Kosmale | Comments As you might know, Qt has a metatype system which provides run-time dynamic information about types. 0. This requires the exchanged data to be of a type that is recognizable by the engine. You could try using registerConverter () to allow implicit conversion of the shared_ptr<int> to a regular int, and compare them that way. If you only want to store pointer to Foo with the metatype system, then use qRegisterMetaType<Foo *> ();. Using Q_ENUM () allows you to retrieve at run-time the name of an enum value: The class in Qt responsible for custom types is QMetaType. qRegisterMetaType<QAbstractSocket::SocketState>(); Share. When I try to build our existing. The default value is Data8, i. Q&A for work. Detailed Description. Follow answered Jan 29, 2016 at 11:01. This maybe is not the nicest solution, but it works just fine: Add a property to the wizardpage which contains the QListView and let it return the pointer to the selectionmodel. if the permission has been granted, it continues with the next permission in the list. しかし、Qtを使っている場合は、わざわざ自分でMutexの管理をしなくても、スレッドとのデータのやり取りを全て signal/slotでやってしまい、共有データを. ) I read on some forum, that this may be caused by calling qt-functions from another Thread, and that using signals & slots instead of plain function calling may fix the issue, but i have tried signals aswell, and i. You only need to call qRegisterMetaType () if the type will be used in queued signal/slots connections, or with the QObject::property API. To not see the message. . 2、使用 qRegisterMetaType，将对象注册为元类型 使用qRegisterMetaType对自. Call qRegisterMetaType() to make type available to non-template based functions, such as the queued signal and slot connections. [since 6. This object can then be passed from QML to C++ via. 12. However, you should verify its validity after construction. You can define one with the enum keyword. Any class or struct that has a. It just allows you to queue types that. It can be done with some global container, but because in C++ order of initializing variables is not defined - it may be not trivial. Returns the internal ID used by QMetaType. It seems QVariant is not direct part of queued connections mechanism. – pmf Feb 7, 2019 at 16:35QObject::connect: Cannot queue arguments of type 'QTextCursor' (Make sure 'QTextCursor' is registered using qRegisterMetaType(). As you have already found out, you must use Q_DECLARE_METATYPE to make the type known to Qt. It seems that for a metatype that is a QList<MyClass::MyEnum> I must. QPainter::begin: Paint device returned engine == 0, type: 3 QPainter::setFont: Painter not active QPainter::setPen: Painter not active [ INFO] [1432901455. There is no use case for implementing qRegisterMetaType, because PyObject. See also qRegisterMetaType(). main. 它的作用是将自定义的数据类型转换为Qt元对象系统中的类型，使得这些类型可以在不同线程之间进行信号槽的传递。. Problem: There is no update of the UI. 5 times (ie. Can you show the code that's actually causing the. Share. ) It's a bit tricky thing. The QObject documentation states that the copy-constructor should be private, but the QMetaType documentation states that a type should have a public default constructor, a public copy constructor, and a public destructor. It seems that for a metatype that is a QList<MyClass::MyEnum> I must. I created a. ) このような場合は以下の通り qRegisterMetaType() の引数を設定することで回避できることがある。You can safely remove the const, even if the real signature of SendData and ReceiveData is const u_char*. Detailed Description. import executer class Window(QtWidegets. Your uint8_t is atomic and you don't need to register it, just use. You could try using registerConverter () to allow implicit conversion of the shared_ptr<int> to a regular int, and compare them that way. The QMetaType class manages named types in the meta-object system. e. Normally you would do this in main () or. Returns true if the Q_PROPERTY () exposes binding functionality; otherwise returns false. The following code allocates and destructs an instance of MyClass:The Q_DECLARE_METATYPE() macro and qRegisterMetaType() function documentation contain more detailed information about their uses and limitations. Usually one puts this (note that the typedefed name is used as string argument): qRegisterMetaType < QSharedPointer < TestClass > > ( "SharedTestClass" );To use the type T in queued signal and slot connections, qRegisterMetaType() must be called before the first connection is established. 2. 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. 2、在类型定义完成后，加入声明：Q_DECLARE_METATYPE (MyDataType); 3、在main ()函数中. Note: Since all expressions evaluated in QML are evaluated in a particular context, if the context is. 用qRegisterMetaType对自定义的类型进行注册，就是为了告诉Qt如何去做这些事情。. The signature of your signal does not match the signature of what you wrote in the SIGNAL macro -- those are non-const references:. 1 Answer. 4 and it seems to work. If it is a partial specialization it might be template<class X> instead. on_click. Teams. That is sad. QtGui. Use Q_DECLARE_OPAQUE_POINTER () to be able to register pointers to forward. call qRegisterMetaType with the name specified, else reading properties. Got the following warnings when running latest code in "develop": QObject::connect: Cannot queue arguments of type 'QTextBlock' (Make sure 'QTextBlock' is registered using qRegisterMetaType(). There was a short discussion about this here. Yet, the first line is invisible and this line becomes visible only if we click on it! Very weird! QObject::connect: Cannot queue arguments of type 'QTextCursor'. (Make sure 'QVector<int>' is registered using qRegisterMetaType (). 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(). This function was introduced in Qt 6. However documentation of qRegisterMetaType() says: "Call this function to. However, I cannot figure out how to verify that the included parameter is FACE_UP or FACE_DOWN. A more complex program sending QSharePointer objects using slots has a similar situation with GDB, that can be reproduced with the previous example. (Make sure 'QVector<QVector<int> >' is registered using qRegisterMetaType (). Call qRegisterMetaType () to make type available to non-template based functions, such as the queued signal and slot connections. So I saw this in the documentation: typedef QString CustomString;. Be very careful as cv::Mat is not implicitly shared, it is just shared (i. You are looking for the Q_ENUM () macro. I tested your code on Qt 5. Although PyQt5 allows any Python callable to be used as a slot when connecting signals, it is sometimes. I pass the MyClass pointer to the streaming operator and only stream things like QString, QPointF, etc. In that case, I think you need to register them. bool QAbstractItemModel:: insertColumn ( int column, const QModelIndex & parent = QModelIndex ()) Inserts a single column before the given column in the child items of the parent specified. Qt Base (Core, Gui, Widgets, Network,. Execute qRegisterMetaType<QItemSelection> (); before it is used as such, e. So I don't stream the pointer itself just copy the properties and set them to a new created pointer object. ) This is hard to track, so I would. 报错提示. 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. And once all of them are updated I'd like the Context object to inform QML to update the view. 11. event – PySide6. QWidget): def __init__(self):. ) but I do not think that relates with the phenomena. A common way to register the type is in main or with a static function register. The constructor does a number of sanity checks, such as verifying that the signal to be spied upon actually exists. In addition to the limitations of the variadic invoke() overload, the arguments must have the same type as the ones expected by the method, else, the behavior is. QtGui import * from PyQt5. Qt documentation specifically states that qRegisterMetaType<T>() must be called for a type to work in the Qt property system. metaObject()->method(functionIndex); qDebug() << mm. cpp; so you will have. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. ) QObject::connect: Cannot queue arguments of type 'QVector<int>' (Make sure 'QVector<int>' is registered using qRegisterMetaType(). This event handler can be reimplemented in a subclass to receive child events. emit() self. the type name must be specified without the class, as in. Call qRegisterMetaType () to make types available to non-template based functions, such as the queued signal and slot connections. 0. This feature is commonly used by proxy connections for virtual connection settings. qRegisterMetaType<foo::FooState>(); Question. Following this logic, the following code may not work: connect (senderObject. All documented Qt functions listed alphabetically with a link to where each one is declared. Normally it's done directly in the main () How: Just call qRegisterMetaType<QMap<QString,long long unsigned int> > (); It doesn't matter how you refer to MyClass in the template argument. Currently, on Linux and Android it is used for specifying connection to a server listening to a socket bound to an abstract address. " and: "Warning: This function is useful only for registering an alias (typedef) for every other use case Q_DECLARE_METATYPE and qMetaTypeId() should be used instead. 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). By convention, these files are given a . For example, let's suppose that we have three. uint8_t is the typedef for unsigned char . From the docs: int qRegisterMetaType ( const char * typeName ) Registers the type name typeName to the type T. ) Bug is reproducable only if a queued connection is used (when objects are in different threads or explicit Qt::QueuedConnection is used) and MyType is declared inside a namespace. Specifically, the function have to be called before using the struct in a queued signal/slot connection or before. ) I believe this is because I am updating the text box from threads other than the ma. . connect(self. 5 and Qt Version 5. The actual values () are either single bit or. qRegisterMetaType<MyStruct>("MyStruct"); 若已经使用 Q_DECLARE_METATYPEQ 标记过该类型，可以使用其不带参数的版本： qRegisterMetaType<MyStruct>(); 同样的，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，如： qRegisterMetaType<NSP::MyStruct>("NSP::MyStruct"); Note that for enum types, you no not even need to call qRegisterMetaType () in these cases. QtのAPIのドキュメントに、thread-safeと書いてない限りは、QMutex等を使って自分で排他をする必要がある。. an int and a std::string. A. It associates a type name to a type so that it can be created and destructed dynamically at. #define. QObject is the heart of the Qt Object Model . When data values are exchanged between QML and C++, they are converted by the QML engine to have the correct data types as appropriate for use in QML or C++. Occurs during "normal" usage (simply adding and downloading. ) It plans for a new trajectory just Okay, but when I try to execute the planned trajectory it gives me the following errors:your struct or simple class must have Q_GADGET as minimum; you should declare properties in order to access from qml; you must declare your struct/class by Q_DECLARE_METATYPE(); you must register it using qRegisterMetaType<>() somewhere before loading qml file by engine such as main. The ones I am registering for are mostly structs for storing data and just a few simple classes. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. Kind Regards, Sy. 048771190]: Out drawPath [ INFO] [1432901455. Toggle Light / Dark / Auto color theme. MainWindow win; win. 错误原因. . Custom types registered using qRegisterMetaType() that have operators for streaming to and from a QDataStream can be stored using QSettings. 二者的联系： QMetaTypeId<TYPE>的类中的成员包含对qRegisterMetaType的调用. Represents a handle to a signal-slot (or signal-functor) connection. I had to uninstall it first, then reinstall it: # upgrade pip python3 -m pip install --upgrade pip # uninstall python3 -m pip uninstall PyQt5 python3 -m pip uninstall PyQt5-sip python3 -m pip uninstall PyQtWebEngine # reinstall python3 -m pip install PyQt5 python3. For the moment, moc will extract and record all tags, but it will not handle any of them specially. Also, to use type T with the QObject::property () API,. For the record your issue come from the fact that Qt preprocessor for signals and slots, the moc, does not use a full-blown C++ parser. ) changing rowCount in the main thread or commenting out setRowCount call in change_row_count() makes those errors. The central feature in this model is a very powerful mechanism for seamless object communication called signals and slots. Since Qt 5. When data values are exchanged between QML and C++, they are converted by the QML engine to have the correct data types as appropriate for use in QML or C++. Registering a metatype shouldn't prevent you from disconnecting a signal. The following code will work similarly: using namespace foo; qRegisterMetaType<MyClass> ("MyClass"); qRegisterMetaType<MyClass> ("foo::MyClass"); For example, the "MyClass" and "foo::MyClass" strings are used to identify argument types when you refer to your signals and slots. See also disconnect(), sender(), qRegisterMetaType(), Q_DECLARE_METATYPE(), and Differences between String-Based and Functor-Based Connections. ). I can override QObject's. The registrations must have happened after doing a foo::FooUsingClass *f = new foo::FooUsingClass();.