The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. 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. ) QObject::connect: Cannot queue arguments of type 'QVector<int>'. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. hi, I always after application running, receive debug text of: QObject::connect: Cannot queue arguments of type 'MyStruct'. There's no compile time error, but when I run. 0. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. 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。. It manages an insane amount of static variables and sets a static global pointer of. typedef QVector<QSharedPointer<Tester> > TestPointerVector;. And once all of them are updated I'd like the Context object to inform QML to update the view. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. "Custom types used by properties need to be registered using the Q_DECLARE_METATYPE() macro so that their values can be stored in QVariant objects. You can 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. [edit] forgot to mention that you also have to use a worker object. 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. I thought there was a bug with QMetaType or Q_DECLARE_METATYPE. . Then you should register your object to use it with QML. There's also no need for that typedef, it only makes the code less readable. // This primary template calls the -Implementation, like all other specialisations should. Call qRegisterMetaType() to make type available to non-template based functions, such as the queued signal and slot connections. With Q_DECLARE_METATYPE and without qRegisterMetaType: No warning, slot is called With Q_DECLARE_METATYPE and with qRegisterMetaType: No warning, slot is called. Qt Code: Switch view. QMetaType. The problem of owner ship of the memory is avoided. So you can call it from your constructor. This function is typically used together with construct () to perform low-level management of the memory used by a type. qRegisterMetaType() requires also a Q_DECLARE_METATYPE() – dtech. Firstly, you shouldn't need to use Q_DECLARE_METATYPE (or qRegisterMetaType) with the enum at all, this is handled by the moc. Type is not registered, please use the Q_DECLARE_METATYPE macro to make it known to Qt's meta-object system. The ENUM type. 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. Qt Base (Core, Gui, Widgets, Network,. The following code will work as well: using namespace foo; Q_DECLARE_METATYPE (MyClass) Teams. I only care about runtime. In the header, after the class declaration, outside the namespace, I've included. QObject::connect: Cannot queue arguments of type 'MyStruct'. Connect and share knowledge within a single location that is structured and easy to search. 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. First of all you need to declare your custom object for Qt metatype system. QMetaType::type () is a bit slower, but compilation succeeds if a type is not registered. This makes them suitable for use with both static properties declared using the Q_PROPERTY() macro in class definitions and dynamic properties created at run-time. See also state(). If you need the functionality provided by Q_DECLARE_METATYPE, you will have to use it. The class is used as a helper to marshall types in QVariant and in queued. For this, a function call (evaluated during runtime) needs to be made, and qRegisterMetatype is the tool for this: qRegisterMetaType<Area>("Area");@julio. Any class or struct that has a public default constructor, a public copy constructor, and a public destructor can be registered. I store them in QVariant :. 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. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. Note that you are technically lying to the meta type system. By the way, Qt 4. Any class or struct that has a public default constructor, a public copy. Q&A for work. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. Qt Remote Objects Compiler. Is your Q_DECLARE_METATYPE in a header file or an implementation file? Incidentally, there is a mistake in TreeItem. h in the translation unit where you have that line. That always worked in Qt4, but in Qt5 I get the following error: @error: specializing member ‘::qRegisterMetaType<Subclass>’ requires ‘template<>’ syntax@. Sorted by: 5. The default access for a class is private, so that Container* data();. I meet a qt metatype issue. QMetaType registerNormalizedTypedef normalizedTypeName, type: metaType ); return. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. J 1 Reply Last reply Reply Quote 0. Normally, you would only register the pointer form if your class cannot be copied, as in the case of QObject and derivatives, but. This allows me to use this type in a Q_PROPERTY, this all. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. QVariant’s operator== now uses QMetaType::equals for the comparison. After googling this, I found this correspondence, which was only available through a third party archival site as google. " Yet types like QVariantMap are themself typedefs. Couple of points: 1) I would use QScriptEngine::newObject() instead of newQObject() for the namespace 2) I would not use a QObject subclass for the data entry if possible, only the prototype has to be. 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. That's created by this macro. Consider the specific case of qRegisterMetaType. I have an application that requires use of both Qt 3D and the QCustomPlot library. Step 1 (mark for MOC), build some QObjects That pattern uses Q_PROPERTY and Q_OBJECT and the MoC tool. You could try using registerConverter () to allow implicit conversion of the shared_ptr<int> to a regular int, and compare them that way. . Connect and share knowledge within a single location that is structured and easy to search. QMetaType Synopsis Functions def __eq__ (b). The object it returns should also be a member of the factory class. Research The QMetaType class manages named types in the meta-object system. h) of the derived class. This article will. 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. Using the following required me to use Q_DECLARE_METATYPE. Q_DECLARE_METATYPE. QObject can't be copied and all its descendants can't be copied also. Good workaround: you may register your type with Q_DECLARE_METATYPE ( IBase * ) macro and wrap your variable. Jul 9, 2017 at 21:51. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. void QAbstractSocket:: abort ()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. Here you can see that the macro expands to nothing. You can make them known ( Q_DECLARE_METATYPE ), however you can't register them as QML type. Q_DECLARE_METATYPE QMetaType::type. It does not say anything about registering the type. qRegisterMetaType usage. 4] QString QWebSocket:: subprotocol const. Qt has to stay free or it will die. qRegisterMetaType you'll need if creating objects by class name dynamically, and it seems for queued connections,. class Test : public QWidget { Q_OBJECT public: Test(); signals: public slots: void setAppData(QList<QIcon> icons, QStringList names, QStringList versions, QStringList publishers, QString installLocation, QStringList uninstallLocations); private: }; Q_DECLARE_METATYPE(QIcon) The same issue is still present. This has been changed, and isNull () now only returns true if the QVariant is empty or contains a nullptr. Than I did read this copy constructor of derived QT class and the answer by BЈовић. # In the class MainWindow declaration #ifndef Q_MOC_RUN # define the tag text as empty,. qRegisterMetaType vs. Q_DECLARE_META_TYPE (Fruit) and qRegisterMetaType were redundant: #define PluginInterface_iid "pluginInterface" Q_DECLARE_INTERFACE (PluginInterface, PluginInterface_iid) //Actual plugin implementing PluginInterface class. But I really would like to know the correct way to solve this problem; one where it is not possible to modify. Thus you need to use the runtime check QMetaType::type (). My workround was to explicitly cast the enum values to int when passing them onto a function requiring a QVariant type, in my case. We all have started by asking questions. More. Q_DECLARE_METATYPE(Pkg) and this does not give compile errors, but in my main. Q_DECLARE_METATYPE(MyClass*); That's how Qt handles it with QObject and QWidget. A separate point for your own benefit. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. If you ever wondered what does Q_DECLARE_META_TYPE or qRegisterMetaType do and when to use (or not to use) them, read on. Greetings. 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. There's also no need for that typedef, it only makes the code less readable. Some structure need to be registered to be queued in asynchronous signals using qRegisterMetaType<T>(name), such as signal which passes QVector<int>. I also don't want to use qRegisterMetaType, since it is run-time bound. Call qRegisterMetaType () to make type available to non-template based functions. 1）引入头文件：#include<QMetaType>. See also. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. Any class or struct that has a public default constructor, a public copy. The logical equivalent of a const T &r (reference to const T) is a const T * const p (const pointer to const T). qRegisterMetaType vs. It associates a type name to a type so that it can be created and destructed dynamically at run-time. The application using it does this: typedef QMap<int, int> MyOtherType; Q_DECLARE_METATYPE (MyOtherType) qRegisterMetaType<MyOtherType> (); Now the D-Bus marshaller and demarshaller get registered with the wrong type id. Share. Original Question. Without this reference, it compiles just fine. With Q_DECLARE_METATYPE and without qRegisterMetaType: No warning, slot is called With Q_DECLARE_METATYPE and with qRegisterMetaType: No warning, slot is called. There's no such thing as a "const reference" because references are always const -- you can't reseat them. 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. // But the split allows to. The docs only talk about class or struct with public default constructor, copy constructor and. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. So, whatever Q_DECLARE_METATYPE is doing cannot be done by writing a function call. Your code should look like this: Q_ENUM (StateEnum) //note the missing 'S' here Q_PROPERTY (StateEnum state READ state NOTIFY stateChanged) Share. Now I want to read this property with Qt's meta object system. I've registered my class with: @Q_DECLARE_METATYPE(MyClass);@ and. 5 is compiled with GCC 4. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. Tried proposed solution using QVariant::fromValue, but kept getting compiler errors of type: . 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. If you want both, then register both. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. To use the type T in QVariant, using Q_DECLARE_METATYPE() is sufficient. If I get AnotherQGadgetClass via getter and change it's properties, the setters are called and. complains that the metatype isn't registered. The Rep lica C ompiler (repc) generates QObject header files based on an API definition file. " –If I declare Class B as follows, it works fine, despite the fact that I haven't done Q_DECLARE_METATYPE for the pointer: #include <QObject> #include <QMetaType> #include "a. To make the custom type. qRegisterMetaType 必须使用该函数的两种情况. 基本理解. Since Qt 5. 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. 1. By convention, these files are given a . 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. Registered enumerations are automatically registered also to the Qt meta type system, making them known to QMetaType without the need to use. I have added Q_DECLARE_METATYPE(quint32) in Class2. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. 3. As a workaround, I'm using QVariantMap instead of std::map. Note that you are technically lying to the meta type system. Per Qt documentation: To use the type T in QVariant, using Q_DECLARE_METATYPE () is sufficient. Q_DECLARE_METATYPE QMetaType::type. Qt is throwing an exception because it doesn't know how to store the shared_ptr onto a QDataStream. no unexpected garbage. It does not say anything about registering the type. The ones I am registering for are mostly structs for storing data and just a few simple classes. But because QUuid stores its content as a QByteArray which is already supported by QVariant, you. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. Once they're known you can use them, but you can't create them on the QML side. Any class or struct that has a public default constructor, a public copy constructor, and a. cpp. qRegisterMetaType vs. Call qRegisterMetaType<std::string> (); in the initialization of your code. It is a static method, it does not (cannot) change x2. The documenation of this macro gives. 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. I think you need to add an explicit export/import directive to the QT_NAMESPACE macro. Q_DECLARE_METATYPE only registers a type in meta type system. Also, to use type T with the QObject::property () API, qRegisterMetaType () must be. 3 to Qt4. 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. Re: Q_DECLARE_METATYPE problem. Additionally Qt5 always refers to Q_DECLARE_METATYPE, saying that qRegisterMetaType is only when you want to. For that, I want to declare a. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. It associates a type name to a type so that it can be created and destructed dynamically at run-time. Then after some time, we can begin answering them. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. call qRegisterMetaType() to register the data type before you establish the connection. 2. }; Q_DECLARE_METATYPE (MyCustomType); Then in my application, I have a signal "void sendMsg (MyCustomType)" and I qRegisterMetaType (). +50. If the type was not declared with Q_DECLARE_METATYPE (), compilation will fail. 如果非QMetaType内置类型要. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. 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. :) QApplication is the root QObject of the program and its full initialization is required before anything can practically be done with anything else. rep file extension, short for Replica. Call qRegisterMetaType() to make type available to non-template based functions, such as the queued signal and slot connections. M. Make your own typedef and do the Q_DECLARE_METATYPE and qRegisterMetatype. Adding a Q_DECLARE_METATYPE () makes the type known to all template based functions, including QVariant. QVariantList , QString (if the list contains exactly one item) Casting between primitive type (int, float, bool etc. x however, the code generated by moc will call qRegisterMetaType for you if moc can determine that the type may be registered as a meta-type. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. EDIT: When you convert your class to QVariant it uses a. qRegisterMetaType vs. As the docs state: Declare new types with Q_DECLARE_METATYPE () to make them available to QVariant and other template-based functions. This also makes the type available for queued. 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. QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). 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. See also disconnect(), sender(), qRegisterMetaType(), Q_DECLARE_METATYPE(), and Differences between String-Based and. As said in int qRegisterMetaType () documentation: To use the type T in QVariant, using Q_DECLARE_METATYPE () is sufficient. Any idea what I'm missing please? BTW, no problem at all using Schedule in QMetaProperty or QVariant. You may have to register before you can post: click the register link above to proceed. To use the type T in QVariant, using Q_DECLARE_METATYPE() is sufficient. the type name must be specified without the class, as in. See the Custom Type Example for code that demonstrates this. See also state() and Creating Custom Qt Types. 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. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. To achieve this you need Q_DECLARE_METATYPE macro and qRegisterMetaType () function. Assuming base and derived are Q_GADGETs you want to get a static member. 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. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. Type is not registered, please use the Q_DECLARE_METATYPE macro to make it known to Qt's meta-object system. There's also no need for that typedef, it only makes the code less readable. See full list on doc. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. So I am doing this: Qt Code: Switch view. If you only want to store pointer to Foo with the metatype system, then use qRegisterMetaType<Foo *> ();. 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. 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. QMetaType::type () is a bit slower, but compilation succeeds if a type is not registered. Because Foo is not derived from QObject and QVariant only supports polymorphism for QObject -derived types. One way to work around this is for example having a helper class (singleton or context property) with. Read and abide by the Qt Code of Conduct. 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. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. This object can then be passed from QML to C++ via Q_INVOKABLE. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. I think it would be great if we could run requests in a QThread, but right now it's not possible because the r. g. without providing the Q_DECLARE_METATYPE macro in the class header, but one could provide a macro where registration is automatically performed (more or less along with meta type declaration). That's created by this macro. cpp. Share. Declare new types with Q_DECLARE_METATYPE () to make them available to QVariant and other template. Call qRegisterMetaType () to make type available to non-template based. I tried and it looks like it's possible to register an enum type with Q_DECLARE_METATYPE or qRegisterMetaType and use it the same way. When the plugin is reloaded later, the old declaration still points to the original memory space of the now-unloaded library. Got a similar example working without explicitly calling qRegisterMetaType() just by removing the semicolon from the line Q_DECLARE_METATYPE(StateMachine::state) – user666412 Sep 21, 2015 at 14:17Additional types can be registered using qRegisterMetaType() or by calling registerType(). [virtual] QAbstractSocket:: ~QAbstractSocket Destroys the socket. Make a typedef for QSharedPointer<UserDataType>, and use both Q_DECLARE_METATYPE as well as qRegisterMetaType () to register it for use. 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. 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. I also added qRegisterMetaType<DataPoint> () to the initialisation method of my main. qt. The. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. x however, the code generated by moc will call qRegisterMetaType for you if moc can determine that the type may be registered as a. 1 Answer. @SGaist Yes, I am using it with QVariant, mostly with QSettings to save and retrieve data easily by overriding QDataStream operators. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. Has anyone else encountered this?See also qRegisterMetaType(). SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). The Q_DECLARE_METATYPE() macro and qRegisterMetaType() function documentation contain more detailed information about their uses and limitations. // This primary template calls the -Implementation, like all other specialisations should. 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. In that case, I think you need to register them. It will return the same result if it was called before. D-Bus offers an extensible type system, based on a few primitive types and associations of them. 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. That was it for Q_DECLARE_METATYPE, but you would still need to call qRegisterMetaType to use these type in a Q_PROPERTY or as a parameter in a signal/slot queued connection. This version of the function is to register alias types. cpp. Declare new types with Q_DECLARE_METATYPE () to make them available to. @Daddedebad As @Bonnie says qRegisterMetaType. QtNetwork. From the docs: int qRegisterMetaType ( const char * typeName ) Registers the type name typeName to the type T. I'm confused by this error, as the documentation states (emphasis mine): Returns the meta type id of type T at compile time. {. See also state() and Creating Custom Qt Types. If the pointer stored in the QVariant can be qobject_cast to T, then that result is returned. 该类型必须有公有的 构造、析构、复制构造 函数. To call qRegisterMetaType (), you still need to use Q_DECLARE_METATYPE (). The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. You may have to register before you can post: click the register link above to proceed. So I played around, copied the original macro and adapted it a bit: @. I have declared all the types with Q_DECLARE_METATYPE, Q_OBJECT and the properties with Q_PROPERTY with the proper getters and setters. Q_DECLARE_METATYPE () doesn't actually register the type; you must still use qRegisterMetaType () for that, particularly if you intend to use the type in signal and slot connections. For pointer types, it also requires that the pointed to type is fully defined. 1 Answer. However, if you want to use a type in a pure runtime context, for example in a QML document, the Qt runtime doesn't know the type declared with Q_DECLARE_METATYPE. void QLocalSocket:: abort ()The signal "orientationChanged" includes an enum of type "Orientation" to indicate if the card has been turned up or down. e. You may have to register before you can post: click the register link above to proceed. Returns the internal ID used by QMetaType. Share Improve this answer Follow answered Jul 23, 2014 at 15:37. It associates a type name to a type so that it can be created and destructed dynamically at run-time. QtCore. The class is used as a helper to marshall types in QVariant and in queued. 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. Re: How to use Q_DECLARE_METATYPE. 1. QLocalSocket. See QMetaType docs for more information. It was also no big issue to call qRegisterMetaType () automatically. It's not enough to get reflection features out of a type this way (it does not create a QMetaObject), so for the thing to be useful at all you need at least Q_GADGET in both base and derived classes. I'm confused by this error, as the documentation states (emphasis mine): Returns the meta type id of type T at compile time. This also makes the type available for queued. Labels: meta system, Meta type, qt. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. See also state () and Creating Custom Qt Types . 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. Avoid having to qRegisterMetaType (pointer. e. 24th July 2010, 09:54 #6. When I emit a signal, then I get next error to the output stream:. QMetaType. by using qRegisterMetaType(). QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). I read a bit and it seems that Q_DECLARE_SMART_POINTER_METATYPE is supposed to allow this to work. 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. The third without Q_DECLARE_METATYPE. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. 1 Answer. Any class or struct that has a public default constructor, a public copy. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. Use Q_DECLARE_OPAQUE_POINTER () to be able to register pointers to forward. Greetings. You don't pass around copies of QObject derived types because it is not copyable. Registers the type name . However, it does appear (at least to me) that you're trying to debug a release build of the application. Using the macro directly turned out to be impossible. 4. 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. 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. 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). cpp. Now, that Q_DECLARE_METATYPE enables the type for Qt template classes and QVariant. staticMetaObject is of type QMetaObject and provides access to the enums declared with Q_ENUMS. Is your feature request related to a problem? No, it's an improvement Please describe. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. To start viewing messages, select the forum that you want to visit from the selection below. no unexpected garbage. You should use Q_DECLARE_METATYPE macro for this. By the way, Qt 4. 1. 2. It associates a type name to a type so that it can be created and destructed dynamically at run-time. 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. qRegisterMetaType vs. qRegisterMetaType vs. Note: it's also safe to call qRegisterMetaType () multiple times. The QMetaType class manages named types in the meta-object system. In some cases in Qt 4, it is also necessary to use the qRegisterMetaType method. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. Improve this answer. [virtual] QAbstractSocket:: ~QAbstractSocket Destroys the socket.