connect(self. For example, setting to 150 results in all characters in the font being 1. Also you may need to use qRegisterMetaType function. qRegisterMetaType <Card::Orientation> ( "Card::Orientation" ); QSignalSpy. If I register QVector I can't dissconnect this signal and the signal is emited. (Parent is QTcpSocket (0x24a6ce8), parent's thread is ServiceSlots. (Make sure 'QVector<int>' is. call qRegisterMetaType with the name specified, else reading properties. Detailed Description. Any class or struct that has a public default constructor, a public copy constructor, and a public destructor can be registered. I'm not sure how to do this in python but probably you should add similar call with QTextCursor. To enable creation of objects at run-time, call the qRegisterMetaType () template function to register it with the meta-object system. You can use Qt's typedef for unsigned char: quint8 and you don't need to register it. (异步调用) Qt::BlockingQueuedConnection，则将以与Qt :: QueuedConnection相同的方式调用该方法，除了当前线程将阻塞直到事件被传递。. QObject::connect: Cannot queue arguments of type 'uint32_t' (Make sure 'uint32_t' is registered using qRegisterMetaType(). Make sure you call it from within a method. If you want both, then register both. 5 and Qt Version 5. Q_DECLARE_METATYPE is only needed for template-based functions. OTOH, passing it by value in lambdas too is dangerous and can cause memory leaks. 因为没有指定 connect的链接方向 Qt::DirectConnection. But the problem comes up when I try to send it to C++ slot, that have my enum as parameter. Otherwise you might be adding duplicate entries to the metatype database each time. 1. No, everything is in separated folders. Undeclared QMetaObject::SuperData. In C++ if you wan't to use some type in queued connection type you should call qRegisterMetaType<MyType> ("MyType"). qRegisterMetaType usage. )" caused by working in threads. G. I'm writing python library for very simple text output to Qt's QTextBrowser window (stored in window. The qRegisterMetaType function essentially allows a typedef or alias to be assigned to a QVariant. – Kamil Klimek. As far as I found before, Qt objects should not be accessed directly. MEMORYSTATUSEX reflects the state of memory at the time of the call. call qRegisterMetaType with the name specified, else reading properties. 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 (in the slot. Now the above code compiles and runs just fine. tag(); // prints MY_CUSTOM_TAG. From Qt documentation: Ideally, this macro should be placed below the declaration of the class or struct. Make sure 'QTextCursor' is registered using qRegisterMetaType(). However, you should verify its validity after construction. This enum was introduced or modified in Qt 5. ) QObject: Cannot create children for a parent that is in a different thread. A QItemSelection is basically a list of selection ranges, see QItemSelectionRange. If you need a socket, you have two options: Instantiate QTcpSocket or QUdpSocket. qRegisterMetaType<QAbstractSocket::SocketState>(); Share. The QMetaType class manages named types in the meta-object system. With Q_DECLARE_METATYPE and without qRegisterMetaType: No warning, slot is called With Q_DECLARE_METATYPE and with qRegisterMetaType: No warning, slot is called. Hm. Usually, we call the macro right below the class/struct declaration in the header file. This requires the exchanged data to be of a type that is recognizable by the engine. In general, you only need Q_DECLARE_METATYPE (). Fixes #46, the logging handler was trying to update a GUI element dir…. But anyway, it is a good practice to use copyable and self-constructable types for stream operators. Instead, the enum should be registered as soon as the shared library is loaded. If a field is empty, don't include it in the result. I am trying to learn Qt and I am attempting to do so by making a little titres game. 13. @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). Be very careful as cv::Mat is not implicitly shared, it is just shared (i. qRe terMetaType 是Qt框架中的一个函数，用于在Qt元对象系统中注册自定义的数据类型。. ) 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. Returns true if the column is inserted; otherwise returns false. The. In the case of this enum, which essentially aliases the int type, it will simply mean that the. Detailed Description. Any class or struct that has a public default constructor, a public copy constructor, and a public destructor can be registered. cpp</code> file implementing <code>YourType</code>. Add a comment | 5 I believe the following is state is not defined in your MyThread class. Now you have a valid QObject. Bachir. // 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. 15. Nov 30, 2012 at 8:31. After about 20 seconds of running LOAM, the laserOdometry module crashes with [laserOdometry-2] process has died [pid 6983, exit code -11, cmd /home/ab. (Parent is QTcpSocket (0x24a6ce8), parent's thread is ServiceSlots. Be very careful as cv::Mat is not implicitly shared, it is just shared (i. This way your metatype will be registered once at startup, and the registration is close by the implementation and does not require to modify <code>main</code>. The QML engine provides built-in support for a. [override virtual noexcept] QQmlEngine:: ~QQmlEngine Destroys the QQmlEngine. However, as you need the type to be. 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. and another folder with the obj files. However, if I add the const qualifier in front of Person* p in the argument list of test () I get errors from QML at run-time! (i. [since 6. newStatuses. Execute qRegisterMetaType<QItemSelection> (); before it is used as such, e. In that case, I think you need to register them. new children are appended at. uint8_t is the typedef for unsigned char . ) changing rowCount in the main thread or commenting out setRowCount call in change_row_count() makes those errors. multithreaded software and I am getting the warning says: (Make sure 'QVector<int>' is registered using qRegisterMetaType (). QObject::connect: Cannot queue arguments of type 'QModbusDevice::State' (Make sure 'QModbusDevice::State' is registered using qRegisterMetaType (). See also convert(). It can be done with some global container, but because in C++ order of initializing variables is not defined - it may be not trivial. ) QObject::connect: Cannot queue arguments of type 'QVector<int>'. goocreations 12 Mar 2013, 07:22. 4 and it seems to work. 1 Answer. For example, let's suppose that we have three. 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。. There was a short discussion about this here. 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. 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。. The Windows registry and INI files use case-insensitive keys, whereas the CFPreferences API on macOS and iOS uses case. v. template<class T> QMetaObject::Connection connect_from_pointer ( const QSharedPointer<T>& sender,. qmlRegisterType<Person> ("People", 1,0, "Person"); This would register the C++ class "Person" as a QML element also called "Person", into the module "People" under the version 1. An alternative would be to wrap shared_ptr<int> in your own class and implement comparison the way you want. For a signal-functor connection without a context object, it is the only way to selectively disconnect that connection. Without this binding click will result in no action. Tour Start here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this siteThis macro is used to specialise the template class QMetaTypeId with typename TYPE, in which, a static member function qt_metatype_id () is defined. king_nak king_nak. Detailed Description. Writes value as the property's value to the given gadget. rep file extension, short for Replica. Re: How to use Q_DECLARE_METATYPE. 2 @Alfredocubitos would it be possible to share an example of the threaded websocket. So, what is the right way to get rid from: QObject::connect: Cannot queue arguments of type 'QTextCursor' (Make sure 'QTextCursor' is registered using qRegisterMetaType (). ICS ICS. We have a couple projects that we developed using Visual Studios 2017, VisualGDB Vers 5. @SGaist Yes, I am using it with QVariant, mostly with QSettings to save and retrieve data easily by overriding QDataStream operators. ) I have defined MyStruct in an accessible header file: myheader. qRegisterMetaType () is called to register the TYPE and generate a TYPE ID. The difference between Qt::QueuedConnection and Qt::AutoConnection is due to a difference in the. Call qRegisterMetaType () to make type available to non-template based. metaObject()->indexOfSlot("testFunc ()"); QMetaMethod mm = win. 3k 33 33 silver badges 58 58 bronze badges. Type names can be registered with QMetaType by using either qRegisterMetaType () or registerType (). Consider the specific case of qRegisterMetaType. ) but I do not think that relates with the phenomena. If the signal is being emitted, I get this error: @. Jun 13, 2021 at 19:37. 2 Answers. As you have already found out, you must use Q_DECLARE_METATYPE to make the type known to Qt. I have a C++ class called MyClass. uint8_t is the typedef for unsigned char . Instead, the following lines have been added to the adding. So I saw this in the documentation: typedef QString CustomString;. Using the macro directly turned out to be impossible. A QItemSelection describes the items in a model that have been selected by the user. 1. To do this you first subclass logging. " Currently I have no UI implemented (yet!). Currently, on Linux and Android it is used for specifying connection to a server listening to a socket bound to an abstract address. I pass the MyClass pointer to the streaming operator and only stream things like QString, QPointF, etc. A common way to register the type is in main or with a static function register. The only changes were made to initArgs and appendArgs functions. ) I have Googled for eons trying to figure out a way how to use the qRegisterMetaType() in PySide, to no avail. My first intuition was to have a class inheriting from rclcpp::Node only with an instance of MainWindow but didn't manage to have it work that way. Readers will master both the C++ language and Qt libraries,. The actual values () are either single bit or. Qt 避免使用qRegisterMetaType（指针与引用），关注常量,qt,Qt,发出信号： void dbConnected(const QSqlDatabase &db); 我从中学到了如何避免使用 qRegisterMetaType<QSqlDatabase>("QSqlDatabase"); 在吃角子老虎的那一边，我会用这样的东西： void onDBConnected(QSqlDatabase * const db); 我关心的是db的使用（正. Reply Quote 0. ) This is hard to track, so I would. class QtGuiApplication : public QWidget { Q_OBJECT public: explicit QtGuiApplication (QWidget *parent = 0. . The file (called a "rep" file) uses a specific (text) syntax to describe the API. You should place Q_DECLARE_METATYPE (QSqlRecord) in only one header and then just include it everywhere it is needed. QAbstractSocket is the base class for QTcpSocket and QUdpSocket and contains all common functionality of these two classes. 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 (). ) Is this a reminder t. Tested on Linux Ubuntu. For the moment, moc will extract and record all tags, but it will not handle any of them specially. From the QVariant::operator== documentation. 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. Hello, Can someone tell me about how to register a metatype in pyqt5. You could also Q_DECLARE_METATYPE to register your custom type and then use qMetaTypeId () to get the metaType id. ) which are updated by simulation code. Put a <code>static MetaTypeRegistration<YourType> registration;</code> in the <code>. SIGNAL(ueSignalTaskFinished(UePosCommProtocolArch::UeCommand&, // reference QByteArray&)), //dittoCustom types registered using qRegisterMetaType() that have operators for streaming to and from a QDataStream can be stored using QSettings. FollowThis can be made to work but it turns out there's a bit of manual labour to be done. 138: 139: This example shows a typical use case of Q_DECLARE_METATYPE(): 140: 141 snippet code/src_corelib_kernel_qmetatype. . Make sure 'QTextCursor' is registered using qRegisterMetaType(). rep file extension, short for Replica. Registering a metatype shouldn't prevent you from disconnecting a signal. 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. 2D Graphics #. If I register QVector I can't dissconnect this signal and the signal is emited. QObject::connect: Cannot queue arguments of type 'QVector<int>' (Make sure 'QVector<int>' is registered using qRegisterMetaType(). g. 1 Reply Last reply 0. 1. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. 11. These are the top rated real world C++ (Cpp) examples of qmlRegisterUncreatableMetaObject extracted. ; Create a native socket descriptor, instantiate QAbstractSocket, and call setSocketDescriptor() to wrap the native socket. 3. 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 can use the tags to annotate your methods. Every second this 2d array is changed by a thread (representing the passage of time) and then this thread emits a signal telling the main GUI to update based on the new game board. error C2059: syntax error : 'string' warning C4667: 'int qRegisterMetaType (void)' : no function template defined that matches forced. 错误原因. 根据类型名. Sets the factory to use for creating QNetworkAccessManager (s). a copy of a cv::Mat object will point to the same data as the copied from item). A single QMetaObject instance is created for each QObject subclass that is used in an application, and this instance stores all the meta-information for the QObject subclass. 二者的联系： QMetaTypeId<TYPE>的类中的成员包含对qRegisterMetaType的调用. 我们知道类中的成员函数并不一定会被调用 (即，该宏并不确保类型被注册到MetaType)。. Handler. Someone may be able to correct me here, but I don't think you should be needing to register the type int&. ) When I do . Thanks for replying! I'm using Qt 5. 2 @Alfredocubitos would it be possible to share an example of the threaded websocket. QtCore import QObject works. QAbstractSocket is the base class for QTcpSocket and QUdpSocket and contains all common functionality of these two classes. I also have to implement for cv::Mat type data. ", which suggests it is only for classes and structs. 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(). 14. There's no compile time error, but when I run. h. How to properly use qRegisterMetaType on a class derived from QObject? I couldn't understand from the answer to where I have to define the specialization of qMetaTypeConstructHelper. Any class or struct that has a public default constructor, a public copy constructor, and a public destructor can be registered. Detailed Description#. ) What I have done is, declare in the main the qRegisterMetatype but it still complaining. 子线程中：QMap<QString, QString> testMap; emit testSignal(testMap);Call qRegisterMetaType() to make type available to non-template based functions, such as the queued signal and slot connections. Read and abide by the Qt Code of Conduct. 2. Each emission of the signal will append one item to the list, containing the arguments of the signal. First of all, shared_ptr needs an (external, in general) reference counter to be allocated. Section and Key Syntax. qRe gisterMetaType 的函数原型为： ```c++ template < type name T> int. Hello, when I run rviz_sim. 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。. @RIJIK "very unlikely" doesn't mean never ever. void QVariant:: clear (). QNetworkAccessManager is used for all network access by QML. 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. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. Qt Base (Core, Gui, Widgets, Network,. QtCore. I'm using Qt 5. But this is all useless if you are not using templates. 2 Answers Sorted by: 3 You do not need to call qRegisterMetaType () to use a type with QVariant. This implies that you can create bindings that use this property as a dependency or install QPropertyObserver objects on this property. QObject is the heart of the Qt Object Model . I created a. The central feature in this model is a very powerful mechanism for seamless object communication called signals and slots . Kind Regards, Sy. ) QObject: Cannot create children for a parent that is in a different thread. (Parent is QTcpSocket (0x24a6ce8), parent's thread is ServiceSlots (0xea66488), current thread is QThread (0x2418a78) See also qRegisterMetaType(). When sender and receiver objects do not live in the same thread, the Qt::QueuedConnection type is used. Registration is not required for most operations; it’s only required for operations that attempt to resolve a type name in string form back to a QMetaType object or the type’s ID. Call qRegisterMetaType () to make type available to non-template based functions, such as the queued signal and slot connections. One of the overloads is a function template that can be used to create an alias for a type and the form is:. 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. For the moment, moc will extract and record all tags, but it will not handle any of them specially. Although you can just create QBluetoothDeviceInfo objects on your own and fill them with data, the easier way is to use the QBluetoothDeviceDiscoveryAgent to start an automated search for visible Bluetooth devices within the connectable range. The following code allocates and destructs an instance of MyClass: To use the type T in queued signal and slot connections, qRegisterMetaType<T>() must be called before the first connection is established. Thanks for the code snippet. ) Nothing special is printed to the execution log. PySide2. ) 1 stopped. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. the type name must be specified without the class, as in. Returns QPartialOrdering::Unordered if comparison is not supported or the values are unordered. 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. 12. If you use queued connections, you'll need to call qRegisterMetaType() too. 1 Answer. ui. 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++. I read on documentation that Q_DECLARE_METATYPE makes available type to QVariant, for example (I got it from documentation): @ struct MyStruct { int i;. Toggle table of contents sidebar. tabs. It is part of QMetaType, which is not implemented by PySide. 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(). Although I have not made clear the specific meaning, at least it can work well. main. My computer was updated and I needed to reinstall all the above tools. In short, I get following error: QObject::connect: Cannot queue arguments of type 'cv::Mat' (Make sure 'cv::Mat' is registered using qRegisterMetaType (). ) @. How to install PyQt5 in Python3. The QItemSelection class is one of the Model/View Classes and is part of Qt’s. Finds signal and returns its index; otherwise returns -1. button. Any class or struct that has a public constructor, a public copy constructor, and a public destructor can be registered. . qRegisterMetaType<geometry_msg::msg::Pose>(); // In MainWindow's constructor. Where: before using any of the above. ) QObject::connect: Cannot queue arguments of type 'QTextCursor' (Make sure 'QTextCursor' is registered using qRegisterMetaType(). As explained in this thread you can try using a typedef, including the QMetaType header and then using both Q_DECLARE_METATYPE macro and the qRegisterMetaType function (as implied by this thread on a similar issue). Normally you would do this in main () or. 5. The QML engine provides built-in support for a. main. You could try using registerConverter () to allow implicit conversion of the shared_ptr<int> to a regular int, and compare them that way. I guess it's the qRegisterMetaType () call itself that's missing. When a new folder is selected I load the thumbnails and. Detailed Description. tag(); // prints MY_CUSTOM_TAG. And this should be used for each exe/dll instance. ; Create a native socket descriptor, instantiate QAbstractSocket, and call setSocketDescriptor() to wrap the native socket. The QScriptValue class provides functions for converting the result. iv. Call qRegisterMetaType<std::string> (); in the initialization of your code. runtime barfs if the signature for test in both headers and . qRegisterMetaType<foo::FooState>(); Question. h. I'm getting this message in the application output pane in Qt Creator running Qt 5. E. 报错提示. Problem: There is no update of the UI. Normally, you would only register the pointer form if your class cannot be copied, as in the case of QObject and derivatives, but. Detailed Description. I don't really know what I have to do in addition. the connect () call returns true, but when the signal is emitted, Qt outputs this: QObject::connect: Cannot queue arguments of type 'uint64'. This function requires that T is a fully defined type at the point where the function is called. . Call qRegisterMetaType() to make type available to non-template based functions, such as the queued signal and slot connections. ) 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*. Share. This also makes the type available for queued signal-slot communication as long as you call it before you make the first connection that uses the type. ) Run a loop on your C++ list and call the append function of qml to add all that data into qml list as well. QML has a signal and handler mechanism, where the signal is the event and the signal is responded to through a signal handler. (Parent is QTextDocument (0x5a28e48), parent's thread is QThread (0x8dbcc0), current thread is QThread. Object::connect: No such slot main_application::input_handler(button_back) Of course, there is, because signature is main_application::input_handler(button_type), and button_back is a value, not type. 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 (). In this case, PyQt will just create a new signal type for you on the fly when you emit the signal. I created a. Teams. Returns true if the Q_PROPERTY () exposes binding functionality; otherwise returns false. – pmf Feb 7, 2019 at 16:35 QObject::connect: Cannot queue arguments of type 'QTextCursor' (Make sure 'QTextCursor' is registered using qRegisterMetaType(). I found a solution for my problem: First create a new header file called enums. 23. This also makes the type available for queued. an int and a std::string. constData ()), " qRegisterNormalizedMetaType ", " qRegisterNormalizedMetaType was called with a not normalized type name, please call qRegisterMetaType instead. 2] enum QLocalSocket:: SocketOption flags QLocalSocket:: SocketOptions This enum describes the possible options that can be used to connect to a server. The Qt doc on qRegisterMetaType explicitly says : T must be declared with Q_DECLARE_METATYPE (). program exits if. So using qRegisterMetaType () you will just trade Q_ENUM () for Q_DECLARE_METATYPE (). In this __init__ we create the QPlainTextEdit that will contain the logs. h which looks like: #ifndef ENUMS_H #define ENUMS_H #include <QtDBus> #include "enumDBus. show(); int functionIndex = win. A. complains that the metatype isn't registered. This class is registered as an uncreatable type so it can be referred by name in QML. The central feature in this model is a very powerful mechanism for seamless object communication called signals and slots. I can override QObject's. 4 x64, and PyQt5 using its binary provided on riverbankcomputiong. – folibis. If you are using queued connections, you need to register std::string as meta type. ) QObject::connect: Cannot queue arguments of type 'QList' (Make sure 'QList' is registered using qRegisterMetaType(). bool QMetaProperty:: writeOnGadget ( void * gadget, const QVariant & value) const. Qt::QueuedConnection，则会发送一个QEvent，并在应用程序进入主事件循环后立即调用该成员。. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. 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. And then Python crashes. Wrong code @ QSettings settings; settings. Returns the internal ID used by QMetaType. on_click) binds signal of a button (clicked) to a slot self. This results in access violations. QMetaType:: Q_DECLARE_OPAQUE_POINTER (PointerType) This macro enables pointers to forward-declared types (PointerType) to be registered with QMetaType using either Q_DECLARE_METATYPE() or qRegisterMetaType(). When you think about, there are quite convincing reasons to disallow it implicitly happening. The. QAbstractSocket is the base class for QTcpSocket and QUdpSocket and contains all common functionality of these two classes. Qt is complaining about QObject::connect: Cannot queue arguments of type 'QTextCursor' (Make sure 'QTextCursor' is registered using qRegisterMetaType(). This object can then be passed from QML to C++ via. The following code allocates and destructs an instance of MyClass: Type names can be registered with QMetaType by using either qRegisterMetaType() or registerType(). cpp is void test (const Person* p)) qrc:example. This function should only be used if this is a property of a Q_GADGET. Save yourself the hassle and use QStringList. Note that this only works for QObject subclasses which use the Q_OBJECT macro. If that is. These are syntactically atrocious, but that’s templates for you. One of these objects is a Connection. Read and abide by the Qt Code of Conduct. I have gave you below the basic process for a deletion for example. The ones I am registering for are mostly structs for storing data and just a few simple classes. To make the type known to this class, we invoke the Q_DECLARE_METATYPE () macro on the class in the header file where it is defined: Q_DECLARE_METATYPE(Message); This now makes it possible for Message values to be stored in QVariant objects and retrieved later. QDBusArgument is the central class in the Qt D-Bus type system, providing functions to marshall and demarshall the primitive types. 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. The custom type T needs to be registered in Qt meta-type system in order to be used in e. e.