Any class or struct that has a public default constructor, a public copy. I only care about runtime. QVariantList MyClass::getFooCollection (void) const { QVariantList list; for (const auto& l: fooCollection_) { list. So my first idea:. Therefore I want to use Q_DECLARE_METATYPE (My_Item) and from the documentation I learned that I need a public copy constructor. [since 6. I read on documentation that Q_DECLARE_METATYPE makes available type to QVariant, for example (I got it from documentation): @ struct MyStruct { int i;. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. Detailed Description. For this, a function call (evaluated during runtime) needs to be made, and qRegisterMetatype is the tool for this: qRegisterMetaType<Area>("Area");@julio. Q_DECLARE_META_TYPE (Fruit) and qRegisterMetaType were redundant: #define PluginInterface_iid "pluginInterface" Q_DECLARE_INTERFACE (PluginInterface, PluginInterface_iid) //Actual plugin implementing PluginInterface class. Avoid having to qRegisterMetaType (pointer. Q_DECLARE_METATYPE on the other hand is (as far as I know) preprocessor bound. Reply Quote. enum Qt:: ContextMenuPolicycall qRegisterMetaType() to register the data type before you call QMetaMethod::invoke(). As the docs state: Declare new types with Q_DECLARE_METATYPE () to make them available to QVariant and other template-based functions. To use the type T in QVariant, using Q_DECLARE_METATYPE() is sufficient. qRegisterMetaType vs. The issue here is that Q_OBJECT forbids the copy and assignment constructors. The struct is declared in my worker class, which is inside a namespace. 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. You can also use QMetaEnum::fromType() to get the QMetaEnum. Consider the specific case of qRegisterMetaType. 9k 9 34 52. ) is supported. 基本理解. Detailed Description The QMetaType class manages named types in the meta-object system. Jun 13, 2021 at 19:37. g. 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. To achieve this you need Q_DECLARE_METATYPE macro and qRegisterMetaType () function. Q_DECLARE_METATYPE QMetaType::type. You may have to register before you can post: click the register link above to proceed. QLocalSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). It looks like one can register a type more than once, specifying different typenames, i. To start viewing messages, select the forum that you want to visit from the selection below. I. 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. Since Qt 5. complains that the metatype isn't registered. We will still need to register it with the meta-object system at run-time by calling the qRegisterMetaType () template function before we make any signal-slot connections that use this type. 该类型必须有公有的 构造、析构、复制构造 函数. qRegisterMetaTypeしているにもかかわらずQObject::connectでランタイムエラーが出る場合の回避策. There's no compile time error, but when I run. It manages an insane amount of static variables and sets a static global pointer of. Your Matrix type is not copiable, thus you can't use Q_DECLARE_METATYPE on it. Qt Remote Objects Compiler. I want to use drag-and-drop to drag a QTreeWidgetItem that has std::shared_ptr user data. 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. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. Improve this answer. To register. Equivalent to Q_DECLARE_METATYPE(TYPE *) and Q_DECLARE_METATYPE(QQmlListProperty<TYPE>) QML_DECLARE_TYPEINFO (Type, Flags) Declares additional properties of the given Type as described by the specified Flags. Posted by Unknown at 2:06 AM. 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. Email This BlogThis! Share to Twitter Share to Facebook Share to Pinterest. The QMetaType class manages named types in the meta-object system. You could try using registerConverter () to allow implicit conversion of the shared_ptr<int> to a regular int, and compare them that way. Actually, they are declared, but in a private section with the macro Q_DISABLE_COPY(). qRegisterMetaType() docs say: Any class or struct that has a public constructor, a public copy constructor, and a public destructor can be registered. ) QObject::connect: Cannot queue arguments of type 'QVector<int>'. Is your Q_DECLARE_METATYPE in a header file or an implementation file? Incidentally, there is a mistake in TreeItem. @SGaist Yes, I am using it with QVariant, mostly with QSettings to save and retrieve data easily by overriding QDataStream operators. 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 (). Type is declared with Q_DECLARE_METATYPE and registered with qRegisterMetaType. The macro will register your variable with the Qt Meta-Object System, which will allow you to. 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. 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(). Q_DECLARE_METATYPE ( blabla* ) Also qRegisterMetaType<T> () is only required for sending your object through queued signal/slot connections. queued connections. qRegisterMetaType vs. But I really would like to know the correct way to solve this problem; one where it is not possible to modify the template classes. 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. See also. and Q_DECLARE_METATYPE uses qRegisterMetaType() internally. Enumerations that are declared with Q_ENUM have their QMetaEnum registered in the enclosing QMetaObject. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. It is not safe to make a QObject's copy constructor public. 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. Is your Q_DECLARE_METATYPE in a header file or an implementation file? Incidentally, there is a mistake in TreeItem. "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. qRegisterMetaType 必须使用该函数的两种情况. 1. 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. cpp. If you want both, then register both. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. You may have to register before you can post: click the register link above to proceed. See also Thread Support in Qt, QObject::connect(), qRegisterMetaType(), and Q_DECLARE_METATYPE(). There's no need to call qRegisterMetaType that many times, once is enough. " –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. your custom type definition. Returns the used WebSocket protocol. 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. 14. in a header file and call @qRegisterMetaType<std::unique_ptr<Thing>> ();@ before your signal and slots are used. 1 Answer. # In the class MainWindow declaration #ifndef Q_MOC_RUN # define the tag text as empty,. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. Can it be Done for a Custom Type? If you really need the qMetatypeId<Type>() to be constexpr, you have to take the responsibility for making it so by specializing struct QMetaTypeId<Type> (or. The following should work: Note that you also have to call qRegisterMetaType<MyMpiMessage> (); before you use the function the first time. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. To start viewing messages, select the forum that you want to visit from the selection below. Duplicate Question(s):Q_DECLARATIVE_METATYPE in and out; Using EventExport vs. 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. The same plugin may be loaded multiple times during the application's lifetime. 4. After googling this, I found this correspondence, which was only available through a third party archival site as google. // 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. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. Q_DECLARE_METATYPE is required to store type with QVariant, those two are required to register object's "big three" to manage it as resource and its serialization methods. To start viewing messages, select the forum that you want to visit from the selection below. The file (called a "rep" file) uses a specific (text) syntax to describe the API. 16. For pointer types, it also requires that the pointed to type is fully defined. Q_DECLARE_METATYPE(MyClass*); That's how Qt handles it with QObject and QWidget. state() Creating Custom Qt Types. View Profile View Forum Posts View Articles Beginner Join Date Nov 2014 Posts 6 Qt products. Sorted by: 5. There's also no need for that typedef, it only makes the code less readable. . Believing an Question from 2010 and the Qt Documentation, the operator==() doesn't work with custom types. QLocalSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). You may have to register before you can post: click the register link above to proceed. 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. 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. 0. You can also use QMetaEnum::fromType() to get the QMetaEnum. qRegisterMetaType vs. I have a const pointer to a class derived from qobject and want to put into QVariant like below: QVariant::fromValue(objectPointer) I have declared the meta type of derived class using: Q_DECLARE_METATYPE(const QDrivedClass *) in the header file (. 2、在类型定义完成后，加入声明：Q_DECLARE_METATYPE (MyDataType); 3、在main ()函数中. Normally, you would only register the pointer form if your class cannot be copied, as in the case of QObject and derivatives, but. 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. g. 8 and it all went well with a few function changes, except I got QMetaProperty::read: Unable to handle unregistered datatype errors all over. Registers the type name . Then you should register your object to use it with QML. ) What I'm trying to do is send a signal containing two cv::Mat images from a QThread to the main thread, so that I can display the output. It would look something like this: Q_DECLARE_METATYPE (MyNamespace::MyClass::MyEnum) However, the Q_DECLARE_METATYPE macro would expand to the following call to qRegisterMetaType: qRegisterMetaType< MyNamespace::MyClass::MyEnum > ("MyNamespace::MyClass::MyEnum",. Q_DECLARE_METATYPE. Good workaround: you may register your type with Q_DECLARE_METATYPE ( IBase * ) macro and wrap your. multithreaded software and I am getting the warning says: (Make sure 'QVector<int>' is registered using qRegisterMetaType (). Make your own typedef and do the Q_DECLARE_METATYPE and qRegisterMetatype. Declare new types with Q_DECLARE_METATYPE () to make them available to. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. Since Qt 5. . : Q_DECLARE_METATYPE(MyClass*); That's how Qt handles it with QObject and QWidget. Does your code ever call qRegisterMetatype() or use Q_DECLARE_METATYPE()? 10th November 2014, 05:23 #3. Normally, you would only register the pointer form if your class cannot be copied, as in the case of QObject and derivatives, but. You had to use QMetaType::registerComparators () and the other static register functions in QMetaType to actually make use of that functionality, though. Declare new types with Q_DECLARE_METATYPE () to make them available to QVariant and other template-based functions. genC last edited by . Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. 4 which does not support all C++11 features. int videoSourceMetaTypeId = qRegisterMetaType< VideoSource > ();Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. Now, that Q_DECLARE_METATYPE enables the type for Qt template classes and QVariant. Make sure you call it from within a method. It associates a type name to a type so that it can be created and destructed dynamically at run-time. Avoid having to qRegisterMetaType (pointer vs reference), concern about const. QVariant’s operator== now uses QMetaType::equals for the comparison. One of these plugins uses Q_DECLARE_METATYPE on some types that need to be stored in a QVariant. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. Q_DECLARE_METATYPE. This object can then be passed from QML to C++ via. 0. cpp. The QML engine provides built-in support for a. Q&A for work. What worries me is that. Q_DECLARE_METATYPE only registers a type in meta type system. Sorted by: 1. void QLocalSocket:: abort ()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. 该类型必须有公有的 构造、析构、复制构造 函数. 4 which does not support all C++11 features. To enable creation of objects at run-time, call the qRegisterMetaType() template function to register it with the meta-object system. QMetaType::type () is a bit slower, but compilation succeeds if a type is not registered. But I couldn't register the type because it's a QObject and I don't have access to the implementation to change it. You pass around pointers instead. Mixing doesn't work but if you always use one or the other it works. By convention, these files are given a . To make the type known to this class, we invoke the Q_DECLARE_METATYPE () macro on the class in the header file where it is defined: Q_DECLARE_METATYPE(Message); This now makes it possible for Message values to be stored in QVariant objects and retrieved later. QMetaType::type () returns the same ID as qMetaTypeId (), but does a lookup at runtime based on the name of the type. 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. no I didn't, do I need to put in the file generated by repc or I can put it anywhere ? – Houss_gc. The QMetaType class manages named types in the meta-object system. Do do you register the meta type with the call qRegisterMetaType("your custom meta type")? 1 Reply Last reply Reply Quote 0. Q_DECLARE_METATYPE(shared_ptr<SomeClass> const &) qRegisterMetaType<shared_ptr<SomeClass> const&>(); 许多标准API都有 QString const & ，因此我认为从根本上来说是可能的，而我只是想不出语法。You actually need to do it once (i. ompiler (repc) generates header files based on an API definition file. 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:. Note that for enum types, you no not even need to call qRegisterMetaType () in these cases. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. Obviously then you would not do registerComparator (). It associates a type name to a type so that it can be created and destructed dynamically at run-time. 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. Declare new types with Q_DECLARE_METATYPE () to make them available. @user6556709 I've added both of those, and it does compile now, but the string is just being default initialized to "" when I call value<T>() and there's a red line under Q_DECLARE_METATYPE that says no instance of overloaded function "qRegisterMetaType" matches the argument list, argument types are: (const char [12],. 1 Answer. QVariantList , QString (if the list contains exactly one item) Casting between primitive type (int, float, bool etc. Any class or struct that has a public default constructor, a public copy constructor, and a. qRegisterMetaType<FileNodePointer> ("FileNodePointer"); should be called once (in main, constructor etc. If you have to use Q_DECLARE_METATYPE yourself, the id is not constexpr. I've registered my class with: @Q_DECLARE_METATYPE(MyClass);@ and. In general, you can only export two kinds of C++ types to QML: QObject-derived classes and some build-in value types, see this documentation page. The default access for a class is private, so that Container* data();. Declare new types with Q_DECLARE_METATYPE () to make them available. 总之，有时候，我们多么希望信号能发送自定义数据类型。. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. In short, I get following error: QObject::connect: Cannot queue arguments of type 'cv::Mat' (Make sure 'cv::Mat' is registered using qRegisterMetaType (). Using the macro directly turned out to be impossible. Research The QMetaType class manages named types in the meta-object system. 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. Re: Q_DECLARE_METATYPE problem. 0. QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). Yes I tried with qRegisterMetaType, it. So using a QString as the type of a Q_PROPERTY only works because it has special built-in support in the QML engine. See also state(). So my first idea:. The Rep lica C ompiler (repc) generates QObject header files based on an API definition file. " and: "Warning: This function is useful only for registering an alias (typedef) for every other use case Q_DECLARE_METATYPE and qMetaTypeId() should be used instead. The other overload around has almost the same form but for the fact that it. @Q_DECLARE_METATYPE (std::unique_ptr<Thing>);@. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. Declare new types with Q_DECLARE_METATYPE () to make them available. 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 (). the type name must be specified without the class, as in. This won't work because you can't use qMetaTypeId<> () before Q_DECLARE_METATYPE<>. 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. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. As a workaround, I'm using QVariantMap instead of std::map. rep file extension, short for Replica. 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. JulienMaille @kshegunov last edited by JulienMaille . h. 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. Make a typedef for QSharedPointer<UserDataType>, and use both Q_DECLARE_METATYPE as well as qRegisterMetaType () to register it for use. @kshegunov said: you're doing it wrong. See also. The following should work: Note that you also have to call qRegisterMetaType<MyMpiMessage> (); before you use the function the first time. 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. Registered enumerations are automatically registered also to the Qt meta type system, making them known to QMetaType without the need to use Q_DECLARE_METATYPE(). So, if you had a custom type FooType, you'd put the Q_DECLARE_METATYPE directly after the declaration, and in. cpp. It associates a type name to a type so that it can be created and destructed dynamically at run-time. ", which suggests it is only for classes and structs. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. To make the custom. call qRegisterMetaType() to register the data type before you establish the connection. The ones I am registering for are mostly structs for storing data and just a few simple classes. i. As a workaround, I'm using QVariantMap instead of std::map. append (QVariant::fromValue (l)); } return list; } The metatype system declaration and registration you have. 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(). So using qRegisterMetaType () you will just trade Q_ENUM () for Q_DECLARE_METATYPE (). We will still need to register it with the meta-object system at run-time by calling the qRegisterMetaType() template function before we make any signal-slot connections that use this type. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. " Currently I have no UI implemented (yet!). Re: Qt warning of type conversion already registered Originally. EDIT: When you convert your class to QVariant it uses a. You can't with Q_GADGETS. struct Matrix { double data [4] [4]; }; Ideally you should be using eigen3. There's also no need for that typedef, it only makes the code less readable. Your code should look like this: Q_ENUM (StateEnum) //note the missing 'S' here Q_PROPERTY (StateEnum state READ state NOTIFY stateChanged) Share. Basically, I created a library containing a type: struct MyCustomType {. h instead ofQVariant x2; x2. hpp and qRegisterMetaType<quint32>("quint32"); in both the Constructors of Class1 and Class2. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. As a workaround you can call the Q_DECLARE_METATYPE macro from the implementation files that need it instead of calling it from the header files, or as the documentation suggests, call it from private headers in each library. Sorted by: 1. See also. It was also no big issue to call qRegisterMetaType () automatically. The QMetaType class manages named types in the meta-object system. The other overload around has almost the same form but for the. 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. Hope it. staticMetaObject is of type QMetaObject and provides access to the enums declared with Q_ENUMS. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. See also. 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. Inheritance diagram of PySide6. // - in a header: // - define a specialization of this template calling an out-of. . In my own code, I use Q_DECLARE_METATYPE for classes I want to store. namespace CCS { Q_DECL_EXPORT Q_NAMESPACE. 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. You could try using registerConverter () to allow implicit conversion of the shared_ptr<int> to a regular int, and compare them that way. The third without Q_DECLARE_METATYPE. That class receives a list of variants (wrapping various data) and converts those variants into a binary stream using QDataStream >. I placed Q_DECLARE_METATYPE (DataPoint) after the class definition. 如果非QMetaType内置类型要. Q_DECLARE_METATYPE, as pointed out by @SingerOfTheFall, would register template based type into QVariant (so it can be retrieved using qvariant_cast<T>()). h" class Context : public QObject { Q_OBJECT Q_PROPERTY (MyGadget* gadget READ gadget CONSTANT) public: explicit Context () : QObject {nullptr} { } MyGadget* gadget () { return &_gadget; } private. Q&A for work. Read and abide by the Qt Code of Conduct. hi, I always after application running, receive debug text of: QObject::connect: Cannot queue arguments of type 'MyStruct'. Here you can see that the macro expands to nothing. The class in Qt responsible for custom types is QMetaType . 2. 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. 0. One of these plugins uses Q_DECLARE_METATYPE on some types that need to be stored in a QVariant. 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. void QAbstractSocket:: abort ()Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. 2 Answers. Using Q_ENUM () allows you to retrieve at run-time. Returns the used WebSocket protocol. (Make sure 'MyStruct' is registered using qRegisterMetaType (). An alternative would be to wrap shared_ptr<int> in your own class and implement comparison the way you want. 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. 8. J. Consider the specific case of qRegisterMetaType. See also state() and Creating Custom Qt Types. 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. Re: How to use Q_DECLARE_METATYPE. 1 Answer. // But the split allows to. QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_REGISTER_METATYPE() and qRegisterMetaType(). Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. このケースでも、Q_DECLARE_METATYPE(QSharedPointer<MyObject>)の宣言と、qRegisterMetatype<QSharedPointer<MyObject>>()の呼び出しが必要になる。 上のサンプルでは、同じsignalに対して2回connectを実行している。 The correct syntax is Q_DECLARE_METATYPE (std::string) without the ;. 0. I read on documentation that Q_DECLARE_METATYPE makes available type to QVariant, for example (I got it from documentation): @ struct MyStruct { int i;. To enable using the type in queued signals and such, there also needs to be a corresponding call: qRegisterMetaType<foo::FooState>(); Question. If \c MyStruct is in a namespace, the Q_DECLARE_METATYPE () macro. Then the TYPE ID is saved in local static vairable metatype_id. To call qRegisterMetaType (), you still need to use Q_DECLARE_METATYPE (). Tried proposed solution using QVariant::fromValue, but kept getting compiler errors of type: . qRegisterMetaType 必须使用该函数的两种情况. canConvert<x> (); } and. Adding a Q_DECLARE_METATYPE () makes the type known to all template based functions, including QVariant. This function was introduced in Qt 4. –To copy to clipboard, switch view to plain text mode. Any class or struct that has a public default constructor, a public copy constructor, and a. I thought there was a bug with QMetaType or Q_DECLARE_METATYPE. Good workaround: you may register your type with Q_DECLARE_METATYPE ( IBase * ) macro and wrap your variable. To use the type T in queued signal and slot connections, qRegisterMetaType () must be called before the first connection is established. The object it returns should also be a member of the factory class. That's probably there, as qRegisterMetaType () wouldn't compile otherwise. 11. It seems that for a metatype that is a QList<MyClass::MyEnum> I must. by using qRegisterMetaType(). const EventExport& in signal and slot profiles; Sending empty EventExport in prepareExport() so emit has no/low data amount; Checking connect statement (always returns true) Having qDebug() in prepareExport() and signal always appears to be emitted; Calling emit right. QVariant::fromValue () returns a QVariant. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. 14. Additional types can be registered using qRegisterMetaType() or by calling registerType(). 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(). 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. The class is used as a helper to marshall types in QVariant and in queued. Add qRegisterMetaType and qDBusRegisterMetaType calls to enable the framework to work with the custom type. Don't use Q_DECLARE_METATYPE and qRegisterMetaType for your QObject enum. 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. 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. You are looking for the Q_ENUM () macro. ) summary refs log tree commit diff statsFoo and Foo* are different types and need to be registered separately. So you can call it from your constructor. But I can't see a method to insert myClass into. QLocalSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). Note: it's also safe to call qRegisterMetaType () multiple times. You'll need Q_DECLARE_METATYPE () if you want to store your type within a QVariant and you will additionally need qRegisterMetaType<> () if you want to dynamically create and destroy objects of that type at runtime, mostly for queued signal and slots connections or the QObject property system. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. 1. 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. Also Q_DECLARE_METATYPE does not register a type, but declares it. Q_DECLARE_METATYPE(TYPEDEF) Q_DECLARE_METATYPE(TYPEDEF) mainwindow. 12. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries that are used. To enable using the type in queued signals and such, there also needs to be a corresponding call: qRegisterMetaType<foo::FooState>(); Question. template <typename T> struct QMetaTypeId<Container<T>>. 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. Macros Detailed Description The QMetaType class manages named types in the meta-object system. But at run time, I got below error:1 Answer. G. 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. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. 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. This won't work because you can't use qMetaTypeId<> () before Q_DECLARE_METATYPE<>. Share. Jul 9, 2017 at 21:51. Make sure you call it from within a method. Quote: bool QVariant::operator==(const QVariant & v) const.