To start viewing messages, select the forum that you want to visit from the selection below. 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. Remember that Q_DECLARE_METATYPE merely defines a specialization of QMetaTypeId for your type. I'm trying to use custom classes in QAbstractListModel, and the Q_DECLARE_METATYPE doesn't work at all! To test where the problem is, I've simplified the code as the following: #include <QMetaType> #include <QVariant> #include <QDebug> typedef int x; Q_DECLARE_METATYPE (x) void main () { QVariant v; qDebug () <<. So my first idea:. The fix is probably to include qsslsocket. Q_DECLARE_METATYPE(MyClass); qRegisterMetaType<MyClass>(); I can use the type in queued connection with signals like this one: void MySignal(MyType o); Now I also would like to use the type with signals like this: void MyVectorSignal(QVector<MyType> v);Qt 5. 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. Then you should register your object to use it with QML. To call qRegisterMetaType (), you still need to use 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. See also. Any class or struct that has a public default constructor, a public copy. . 如果非QMetaType内置类型要. 被 Q_DECLARE_METATYPEQ 标记的类型可以让Q MetaType 查询到类型，也可以让QVariant识别到。 struct MyStruct { QString name; }; Q_DECLARE_METATYPE(MyStruct) 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. no unexpected garbage data or the like). 2）添加声明：利用宏 Q_DECLARE_METATYPE. There is no contradiction, because you can't register QObject descendants with Q_DECLARE_METATYPE. 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. Jul 9, 2017 at 21:51. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. // 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. Here you can see that the macro expands to nothing. See also state() and Creating Custom Qt Types. Q_DECLARE_METATYPE (std::string) Quoting Qt Doc. Because Foo is not derived from QObject and QVariant only supports polymorphism for QObject -derived types. QVariant x2 = QVariant::fromValue( x1); To copy to clipboard, switch view to plain text mode. 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. However, I cannot figure out how to verify that the included parameter is FACE_UP or FACE_DOWN. Read and abide by the Qt Code of Conduct. QVariant v = QVariant::fromValue<cMyClass>(MyObject); However, as soon as I use Q_DECLARE_METATYPE, I get errors about using a deleted function. qRegisterMetaType() docs say: Any class or struct that has a public constructor, a public copy constructor, and a public destructor can be registered. More. e. The class in Qt responsible for custom types is QMetaType . 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. Q_DECLARE_METATYPE(MyStruct) Q_DECLARE_METATYPE(MyList) QDBusArgument &operator<<(QDBusArgument &, const MyStruct&);. 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. You could try using registerConverter () to allow implicit conversion of the shared_ptr<int> to a regular int, and compare them that way. typedef QVector<QSharedPointer<Tester> > TestPointerVector;. cpp. Custom Type Qlist and Scope. h. Now, that Q_DECLARE_METATYPE enables the type for Qt template classes and QVariant. qRegisterMetaType<signed long long>() - do nothing. QList<AnotherObject*> has of course been registered with Q_DECLARE_METATYPE and qRegisterMetaType(). 【2】使用方法（声明 和 注册自定义数据类型）. Declare new types with Q_DECLARE_METATYPE () to make them available to QVariant and other template. It's a bit convoluted to follow, and definitely depends on which Qt modules have been included (the meta type system is designed to be expandable this way -- eg. So using a QString as the type of a Q_PROPERTY only works because it has special built-in support in the QML engine. Q&A for work. G. An alternative would be to wrap shared_ptr<int> in your own class and implement comparison the way you want. My workround was to explicitly cast the enum values to int when passing them onto a function requiring a QVariant type, in my case when adding a QComboBox item, and then casting it back to my enum class type at value retrieval. Q_DECLARE_METATYPE(Pkg) and this does not give compile errors, but in my main. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. Qt Base (Core, Gui, Widgets, Network,. 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. h" class B : public QObject { Q_OBJECT Q_PROPERTY(A* A1 READ getA1 WRITE setA1) Q_PROPERTY(A* A2 READ getA2 WRITE setA2) public: static A A1;. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. " Currently I have no UI implemented (yet!). 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. If \c MyStruct is in a namespace, the Q_DECLARE_METATYPE () macro. e. 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. Without this reference, it compiles just fine. Additionally Qt5 always refers to Q_DECLARE_METATYPE, saying that qRegisterMetaType is only when you want to. Teams. Q_DECLARE_METATYPE. qRegisterMetaType vs. Note: it's also safe to call qRegisterMetaType () multiple times. But because QUuid stores its content as a QByteArray which is already supported by QVariant, you. Q_DECLARE_METATYPE on the other hand is (as far as I know) preprocessor bound. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. But at run time, I got below error:1 Answer. For that, I want to declare a. That. e. So I am doing this: Qt Code: Switch view. 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. 0. QLocalSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). S 1 Reply Last reply Reply Quote 0. If you want both, then register both. Q_DECLARE_METATYPE. This article will. in a header file and call @qRegisterMetaType<std::unique_ptr<Thing>> ();@ before your signal and slots are used. To use the type T in queued signal and slot connections, qRegisterMetaType<T>() must be called before the first connection is established. [since 6. The correct syntax is Q_DECLARE_METATYPE (std::string) without the ;. The id is constexpr in the special case of Qt built-in types only. [override virtual] bool QAbstractSocket:: waitForBytesWritten (int msecs = 30000) Reimplements:. See also. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. The ones I am registering for are mostly structs for storing data and just a few simple classes. Although I'm. Registers the type name . But I couldn't register the type because it's a QObject and I don't have access to the implementation to change it. To start viewing messages, select the forum that you want to visit from the selection below. template <typename T> struct QMetaTypeId<Container<T>>. This macro is used to specialise the template class QMetaTypeId with typename TYPE, in which, a static member function qt_metatype_id () is defined. 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. Sorted by: 5. Alt. 0. So I don't stream the pointer itself just copy the properties and set them to a new created pointer object. To enable creation of objects at run-time, call the qRegisterMetaType() template function to register it with the meta-object system. 被 Q_DECLARE_METATYPEQ 标记的类型可以让Q MetaType 查询到类型，也可以让QVariant识别到。 struct MyStruct { QString name; }; Q_DECLARE_METATYPE(MyStruct) 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. Using Q_ENUM () allows you to retrieve at run-time the name of an enum value: Q_GADGET makes a class member, staticMetaObject, available. Read and abide by the Qt Code of Conduct. You may have to register before you can post: click the register link above to proceed. 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. [quote author="Andre" date="1306394817"]In that case, I think you need to register them. In the example's Message class, a static method is included to do this. As G. Detailed Description. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. From the docs: int qRegisterMetaType ( const char * typeName ) Registers the type name typeName to the type T. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. Jun 13, 2021 at 19:37. Returns the metatype of the parameter at the given index. Qt Code: Switch view. hpp and qRegisterMetaType<quint32>("quint32"); in both the Constructors of Class1 and Class2. Execute qRegisterMetaType<QItemSelection> (); before it is used as such, e. There's no need to call qRegisterMetaType that many times, once is enough. Q_DECLARE_METATYPE QMetaType::type. The Rep lica C ompiler (repc) generates QObject header files based on an API definition file. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. 5 is compiled with GCC 4. But this is all useless if you are not using templates. This allows us to use the Enum as a custom-type of a QVariant, to pass it between QML and Qt, to use it in synchronous signal-slot connections, and to print the symbolic enums (instead of a magic number) with qDebug(). Read and abide by the Qt Code of Conduct. J 1 Reply Last reply Reply Quote 0. QMetaType::type () is a bit slower, but compilation succeeds if a type is not registered. See also Thread Support in Qt, QObject::connect(), qRegisterMetaType(), and Q_DECLARE_METATYPE(). namespace CCS { Q_DECL_EXPORT Q_NAMESPACE. Q_DECLARE_METATYPE(Pkg) and this does not give compile errors, but in my main. rep file extension, short for Replica. 该类型必须有公有的 构造、析构、复制构造 函数. +50. Franzk 26 May 2011, 06:59. 4] QString QWebSocket:: subprotocol const. Obviously then you would not do registerComparator (). To use the type T in queued signal and slot connections, qRegisterMetaType<T>() must be called before the first connection is established. Macros Detailed Description The QMetaType class manages named types in the meta-object system. 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. qRegisterMetaType<Subclass> ("Subclass") also doesn't work. This function was introduced in Qt 4. But I can't see a method to insert myClass into. Assuming base and derived are Q_GADGETs you want to get a static member. Learn more about Teams Declaring a meta type. I'm confused by this error, as the documentation states (emphasis mine): Returns the meta type id of type T at compile time. [override virtual] bool QLocalSocket:: waitForBytesWritten (int msecs = 30000) Reimplements:. Since Qt 5. Declare new types with Q_DECLARE_METATYPE () to make them available to QVariant and other template. Good workaround: you may register your type with Q_DECLARE_METATYPE ( IBase * ) macro and wrap your. So in your case you need to declare. The problem of owner ship of the memory is avoided. {. In Qt, you can declare a variable in two ways: 1. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. QML Qvariant from custom class. You may have to register before you can post: click the register link above to proceed. To use the type T in queued signal and slot connections, qRegisterMetaType<T>() must be called before the first connection is established. Q_DECLARE_METATYPE(TYPEDEF) Q_DECLARE_METATYPE(TYPEDEF) mainwindow. See also state(). 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. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. To start viewing messages, select the forum that you want to visit from the selection below. Use Q_DECLARE_OPAQUE_POINTER () to be able to register pointers to forward. I have registered an enumeration type "ClefType" within my header file - this enum is registered with the MetaObject system using the Q_DECLARE_METATYPE and Q_ENUMS macros. As a workaround, I'm using QVariantMap instead of std::map. If you want to pass IBase * between different threads, you need to register class with qRegisterMetaType<IBase *> () call; It is bad practice to pass pointers throught singals, because it is hard to control lifetime of passed objects. Usually it goes in a pair: Q_DECLARE_METATYPE(TypeName) goes in the header, and then in the source at runtime registration is done with: qRegisterMetaType<TypeName>();answered May 10, 2013 at 2:25. @SGaist Yes, I am using it with QVariant, mostly with QSettings to save and retrieve data easily by overriding QDataStream operators. I am also using some in queued signal and slot connections. As said in int qRegisterMetaType () documentation: To use the type T in QVariant, using Q_DECLARE_METATYPE () is sufficient. M. Using Qt 3D with QCustomPlot. But there would be no trouble using the QMetaType class or using qRegisterMetaType before creating an instance of QCoreApplication or QApplication. int videoSourceMetaTypeId = qRegisterMetaType< VideoSource > ();QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). Declare new types with Q_DECLARE_METATYPE () to make them available. qRegisterMetaType() requires also a Q_DECLARE_METATYPE() – dtech. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. Use Q_DECLARE_METATYPE (std::string) in one of your headers. QVariantList MyClass::getFooCollection (void) const { QVariantList list; for (const auto& l: fooCollection_) { list. 3 to Qt4. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. According to the Qt docs for qRegisterMetaType "Any class or struct that has a public default constructor, a public copy constructor, and a public destructor can be registered. The Custom Type and Queued Custom Type examples show how to implement a custom type with the features outlined in this document. The reason to need this is usually that Q_PROPERTY is used with a metatype which is not built-in (types such as int and QString are built-in and don’t. Constantin. This allows me to use this type in a Q_PROPERTY, this all. The. 0. There's also no need for that typedef, it only makes the code less readable. h in the translation unit where you have that line. append (QVariant::fromValue (l)); } return list; } The metatype system declaration and registration you have. 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). 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. Q_DECLARE_METATYPE, as pointed out by @SingerOfTheFall, would register template based type into QVariant (so it can be retrieved using qvariant_cast<T>()). I have an application that requires use of both Qt 3D and the QCustomPlot library. 2. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries that are used. There's no need to call qRegisterMetaType that many times, once is enough. 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. This function is typically used together with construct () to perform low-level management of the memory used by a type. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. If you want both, then register both. Ah, sorry, I didn't noticed that part. You may have to register before you can post: click the register link above to proceed. So you can call it from your constructor. From the docs: int qRegisterMetaType ( const char * typeName ) Registers the type name typeName to the type T. 4. Re: How to use Q_DECLARE_METATYPE. in a header file and call @qRegisterMetaType<std::unique_ptr<Thing>> ();@ before your signal and slots are used. If the type was not declared with Q_DECLARE_METATYPE (), compilation will fail. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. 1 Answer. 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. by using qRegisterMetaType(). hpp which is included in Class1. Q_DECLARE_METATYPE. 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。. The documentation for exposing C++ properties to QML says that: "Note: Do not use typedef or using for Q_PROPERTY types as these will confuse moc. Also Q_DECLARE_METATYPE does not register a type, but declares it. It associates a type name to a type so that it can be created and destructed dynamically at run-time. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. call qRegisterMetaType() to register the data type before you establish the connection. 11. You could try using registerConverter () to allow implicit conversion of the shared_ptr<int> to a regular int, and compare them that way. said, try to directly pass shared_ptr with your signal/slots. 0. The Q_DECLARE_METATYPE() macro and qRegisterMetaType() function documentation contain more detailed information about their uses and limitations. Quote: bool QVariant::operator==(const QVariant & v) const. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. Re: Qt warning of type conversion already registered Originally. QMetaType registerNormalizedTypedef normalizedTypeName, type: metaType ); return. To make the custom type. I created a. That class receives a list of variants (wrapping various data) and converts those variants into a binary stream using QDataStream >. [virtual] QAbstractSocket:: ~QAbstractSocket Destroys the socket. QVariant’s operator== now uses QMetaType::equals for the comparison. qRegisterMetaType vs. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. 基本理解. First of all, you always need to declare your meta type: Q_DECLARE_METATYPE (foo::MyClass) It works at compile time, so there are no limitations on how you refer to your class. The other overload around has almost the same form but for the fact that it. Now you have a valid QObject. Consider the specific case of qRegisterMetaType. Qt has to stay free or it will die. 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. staticMetaObject is of type QMetaObject and provides access to the enums declared with Q_ENUMS. Last updated at 2016-07-08 Posted at 2015-11-16. namespace CCS { Q_DECL_EXPORT Q_NAMESPACE. Is your Q_DECLARE_METATYPE in a header file or an implementation file? Incidentally, there is a mistake in TreeItem. Any class or struct that has a public default constructor, a public copy. SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). 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. Type is not registered, please use the Q_DECLARE_METATYPE macro to make it known to Qt's meta-object system. Some structure need to be registered to be queued in asynchronous signals using qRegisterMetaType<T>(name), such as signal which passes QVector<int>. Yes I tried with qRegisterMetaType, it. Please note that I do not use Q_DECLARE_METATYPE on purpose because I don't actually need its features (QVariant expansion) right now. Obviously then you would not do registerComparator (). This has been changed, and isNull () now only returns true if the QVariant is empty or contains a nullptr. As a workaround, I'm using QVariantMap instead of std::map. canConvert<x> (); } and. 14. @Q_DECLARE_METATYPE (std::unique_ptr<Thing>);@. I haven't used that module yet but one thing you should do is remove the string argument from your qRegisterMetaType calls. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. [virtual] QLocalSocket:: ~QLocalSocket Destroys the socket, closing the connection if necessary. no unexpected garbage. so that was all, but remember to use Q_DECLARE_METATYPE, qRegisterMetaType macros for registering your custom type with Qt meta object system. 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. EDIT: When you convert your class to QVariant it uses a. [virtual] QAbstractSocket:: ~QAbstractSocket Destroys the socket. 2 Answers. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. You pass around pointers instead. 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(). 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. 1）引入头文件：#include<QMetaType>. 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. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. Detailed Description. However, it does appear (at least to me) that you're trying to debug a release build of the application. The QML engine provides built-in support for a. Qt Base (Core, Gui, Widgets, Network,. fromValue <QList<double> > ( x1); To copy to clipboard, switch view to plain text mode. There's no need to call qRegisterMetaType that many times, once is enough. I meet a qt metatype issue. QLocalSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). @Wieland Thanks. 1 Answer. since it is a runtime registration. 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. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. Also, Q_DECLARE_METATYPE(MyNamespace::MyType) should be in the header declaring MyType so that you don't have to repeat it all over again and again. I want to use my objects as QVariants and for queued connections. QMetaType Synopsis Functions def __eq__ (b). You can make them known ( Q_DECLARE_METATYPE ), however you can't register them as QML type. That always worked in Qt4, but in Qt5 I get the following error: @error: specializing member ‘::qRegisterMetaType<Subclass>’ requires ‘template<>’ syntax@. } But you'll most likely need to abstract the Q_DECL_EXPORT part so it is a Q_DECL_IMPORT in right circumstances, as described in Creating Shared Libraries. I read a bit and it seems that Q_DECLARE_SMART_POINTER_METATYPE is supposed to allow this to work. Consider the specific case of qRegisterMetaType. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. 0. i. and Q_DECLARE_METATYPE uses qRegisterMetaType() internally. The following should work: Note that you also have to call qRegisterMetaType<MyMpiMessage> (); before you use the function the first time. Note that you are technically lying to the meta type system. Read and abide by the Qt Code of Conduct. @Daddedebad As @Bonnie says qRegisterMetaType. If you are using queued connections, you need to register std::string as meta type. qt. Call qRegisterMetaType () to make type available to non-template based. To start viewing messages, select the forum that you want to visit from the selection below. enum Qt:: ContextMenuPolicyQObject has neither a copy constructor nor an assignment operator. Did you also check the Q_DECLARE_METATYPE macro ? You should declare and register the types properly, lying to qRegisterMetaType will get you in trouble in the long run. The QMetaType class manages named types in the meta-object system. One of these plugins uses Q_DECLARE_METATYPE on some types that need to be stored in a QVariant. : Q_DECLARE_METATYPE(MyClass*); That's how Qt handles it with QObject and QWidget. 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. To make the custom. When the plugin is reloaded later, the old declaration still points to the original memory space of the now-unloaded library. Research The QMetaType class manages named types in the meta-object system. That's created by this macro. When these files are processed by repc, repc generates both. qRegisterMetaType vs. 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. This worked very well. I also added qRegisterMetaType<DataPoint> () to the initialisation method of my main. 5 is compiled with GCC 4. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. It associates a type name to a type so that it can be created and destructed dynamically at run-time. // This primary template calls the -Implementation, like all other specialisations should. 4. qRegisterMetaType vs. ), or any other callable, cannot declare a type for use outside of the call site. 0. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. See the Qt D-Bus Type System page for more information on the type system. // This primary template calls the -Implementation, like all other specialisations should. G. Share. If you want to pass IBase * between different threads, you need to register class with qRegisterMetaType<IBase *> () call; It is bad practice to pass pointers throught singals, because it is hard to control lifetime of passed objects. 1. 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. I'm trying to use custom classes in QAbstractListModel, and the Q_DECLARE_METATYPE doesn't work at all! To test where the problem is, I've simplified the code as the following: #include <QMetaType> #include <QVariant> #include <QDebug> typedef int x; Q_DECLARE_METATYPE (x) void main () { QVariant v; qDebug () << v. 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. How: I linked qRegisterMetaType. ", which suggests it is only for classes and structs. Any class or struct that has a public default constructor, a public copy. I only care about runtime. To start viewing messages, select the forum that you want to visit from the selection below. It manages an insane amount of static variables and sets a static global pointer of. Connect and share knowledge within a single location that is structured and easy to search. 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. See also state() and Creating Custom Qt Types. 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. 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. 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. QList of Custom Objects. If such a connection is made, and a signal triggered, the runtime warning will be shown: QObject::connect: Cannot. One of these plugins uses Q_DECLARE_METATYPE on some types that need to be stored in a QVariant. Call qRegisterMetaType () to make type available to non-template based functions. According to the Qt docs for qRegisterMetaType "Any class or struct that has a public default constructor, a public copy constructor, and a public destructor can be registered. Declare new types with Q_DECLARE_METATYPE () to make them available to. qRegisterMetaType vs. It associates a type name to a type so that it can be created and destructed dynamically at run-time. @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). Inheritance diagram of PySide6. Sorted by: 1. goocreations 12 Mar 2013, 07:22. qRegisterMetaType<FileNodePointer> ("FileNodePointer"); should be called once (in main, constructor etc. Believing an Question from 2010 and the Qt Documentation, the operator==() doesn't work with custom types. on top of main. The class in Qt responsible for custom types is QMetaType. 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. The same plugin may be loaded multiple times during the application's lifetime. QVariant::fromValue () returns a QVariant. To achieve this you need Q_DECLARE_METATYPE macro and qRegisterMetaType () function. Follow answered Jun 5, 2009 at 15:14. So using qRegisterMetaType () you will just trade Q_ENUM () for Q_DECLARE_METATYPE (). uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. Does your code ever call qRegisterMetatype() or use Q_DECLARE_METATYPE()? 10th November 2014, 06:23 #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. qRegisterMetaType<FileNodePointer> ("FileNodePointer"); should be called once (in main, constructor etc. To register a type, it must be declared as a meta-type with the Q_DECLARE_METATYPE() macro, and then registered as in the following example:. 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. Creating and Destroying Custom Objects 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 class. For pointer types, it also requires that the pointed to type is fully defined. 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.