Jul 9, 2017 at 21:51. From the docs: int qRegisterMetaType ( const char * typeName ) Registers the type name typeName to the type T. Call qRegisterMetaType () to make type available to non-template based. . That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. If you have to use Q_DECLARE_METATYPE yourself, the id is not constexpr. By convention, these files are given a . 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 ;. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. [virtual] QAbstractSocket:: ~QAbstractSocket Destroys the socket. As a workaround, I'm using QVariantMap instead of std::map. Email This BlogThis! Share to Twitter Share to Facebook Share to Pinterest. The issue here is that Q_OBJECT forbids the copy and assignment constructors. e. See also isRegistered () and Q_DECLARE_METATYPE (). Because Foo is not derived from QObject and QVariant only supports polymorphism for QObject -derived types. You can use Q_DECLARE_METATYPE(Widget*) but it is not needed as of Qt. I only care about runtime. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries that are used. QtCore. Jun 13, 2021 at 19:37. There's no need to call qRegisterMetaType that many times, once is enough. . QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). 0. 2 Answers. 1. Read and abide by the Qt Code of Conduct. e. Q_DECLARE_META_TYPE (Fruit) and qRegisterMetaType were redundant: #define PluginInterface_iid "pluginInterface" Q_DECLARE_INTERFACE (PluginInterface, PluginInterface_iid) //Actual plugin implementing PluginInterface class. @Q_DECLARE_METATYPE (std::unique_ptr<Thing>);@. Even though we do not intend. . Q_DECLARE_METATYPE(Pkg) and this does not give compile errors, but in my main. 11. It associates a type name to a type so that it can be created and destructed dynamically at run-time. x however, the code generated by moc will call qRegisterMetaType for you if moc can determine that the type may be registered as a. call qRegisterMetaType() to register the data type before you establish the connection. Returns the internal ID used by QMetaType. Posted by Unknown at 2:06 AM. You have to register your class to Qt meta objects system. I have added Q_DECLARE_METATYPE(quint32) in Class2. Labels: meta system, Meta type, qt. genC last edited by . fromValue <QList<double> > ( x1); To copy to clipboard, switch view to plain text mode. Re: How to use Q_DECLARE_METATYPE. To start viewing messages, select the forum that you want to visit from the selection below. Then after some time, we can begin answering them. There's no need to call qRegisterMetaType that many times, once is enough. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. So, you don't want 'Widget' to be a metatype, you want 'Widget*' to be a metatype so that you can put a Widget* in a QVariant for example. ", which suggests it is only for classes and structs. 5 is compiled with GCC 4. I pass the MyClass pointer to the streaming operator and only stream things like QString, QPointF, etc. 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. I think you need to add an explicit export/import directive to the QT_NAMESPACE macro. {. I however have a scenario where I want to declare such an object in qml and transmit it to the c++. 4] QString QWebSocket:: subprotocol const. type() typeName() PySide6. One of these plugins uses Q_DECLARE_METATYPE on some types that need to be stored in a QVariant. Alt. Qt Remote Objects Compiler. Also Q_DECLARE_METATYPE does not register a type, but declares it. cpp. But at run time, I got below error:1 Answer. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries. To start viewing messages, select the forum that you want to visit from the selection below. Assuming base and derived are Q_GADGETs you want to get a static member. Any class or struct that has a public default constructor, a public copy constructor, and a. qRegisterMetaType vs. The Q_DECLARE_METATYPE() macro and qRegisterMetaType() function documentation contain more detailed information about their uses and limitations. QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). 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. QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). If you are using queued connections, you need to register std::string as meta type. This won't work because you can't use qMetaTypeId<> () before Q_DECLARE_METATYPE<>. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. " –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. 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. 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. 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. Type is not registered, please use the Q_DECLARE_METATYPE macro to make it known to Qt's meta-object system. The class is used as a helper to marshall types in QVariant and in queued. e. Share. 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. I tested your code on Qt 5. 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. If I get AnotherQGadgetClass via getter and change it's properties, the setters are called and. I only care about runtime instantiation. When the plugin is reloaded later, the old declaration still points to the original memory space of the now-unloaded library. 如果非QMetaType内置类型要. It seems that for a metatype that is a QList<MyClass::MyEnum> I must. See also disconnect(), sender(), qRegisterMetaType(), Q_DECLARE_METATYPE(), and Differences between String-Based and. 4 and it seems to work. PySide6. Good workaround: you may register your type with Q_DECLARE_METATYPE ( IBase * ) macro and wrap your variable. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. Call qRegisterMetaType() to make types available to non-template based functions, such as the queued signal and slot connections. You should use Q_DECLARE_METATYPE macro for this. You may have to register before you can post: click the register link above to proceed. in a header file and call @qRegisterMetaType<std::unique_ptr<Thing>> ();@ before your signal and slots are used. namespace CCS { Q_DECL_EXPORT Q_NAMESPACE. This fixed the issue. 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. Make sure you call it from within a method. Q_DECLARE_METATYPE(TYPEDEF) Q_DECLARE_METATYPE(TYPEDEF) mainwindow. qRegisterMetaType vs. Similarly you can create a mutable view of type QAssociativeIterable on any container registered with Q_DECLARE_ASSOCIATIVE_CONTAINER_METATYPE(). I am also using some in queued signal and slot connections. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. 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. qRegisterMetaType vs. append (QVariant::fromValue (l)); } return list; } The metatype system declaration and registration you have. 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. 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. 2 Answers. Re: Q_DECLARE_METATYPE problem. @Q_DECLARE_METATYPE (std::unique_ptr<Thing>);@. // But the split allows to. SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_DECLARE_METATYPE() and qRegisterMetaType(). Sorted by: 3. QMetaType registerNormalizedTypedef normalizedTypeName, type: metaType ); return. 2. . There's also no need for that typedef, it only makes the code less readable. You may have to register before you can post: click the register link above to proceed. Share Improve this answerWe 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. 7. I've registered my class with: @Q_DECLARE_METATYPE(MyClass);@ and. 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. no I didn't, do I need to put in the file generated by repc or I can put it anywhere ? – Houss_gc. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. 0. From the docs: int qRegisterMetaType ( const char * typeName ) Registers the type name typeName to the type T. 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 meet a qt metatype issue. The code compiles and runs ok. Basically, I created a library containing a type: struct MyCustomType {. 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. 2. 基本理解. Since Qt 5. Q_DECLARE_METATYPE. // - in a header: // - define a specialization of this template calling an out-of. 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. 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. Q_DECLARE_METATYPE. Registered enumerations are automatically registered also to the Qt meta type system, making them known to QMetaType without the need to use. It does not say anything about registering the type. The following should work: Note that you also have to call qRegisterMetaType<MyMpiMessage> (); before you use the function the first time. You may have to register before you can post: click the register link above to proceed. 4] QString QWebSocket:: subprotocol const. If the type was not declared with Q_DECLARE_METATYPE (), compilation will fail. The reasoning is found in the. Yes, templated types can be used in Qt signal/slots. When these files are processed by repc, repc generates both Source and Replica header files. With Q_DECLARE_METATYPE and without qRegisterMetaType: No warning, slot is called With Q_DECLARE_METATYPE and with qRegisterMetaType: No warning, slot is called. To enable creation of objects at run-time, call the qRegisterMetaType() template function to register it with the meta-object system. You may have to register before you can post: click the register link above to proceed. :) QApplication is the root QObject of the program and its full initialization is required before anything can practically be done with anything else. staticMetaObject is of type QMetaObject and provides access to the enums declared with Q_ENUMS. QLocalSocket. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. 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. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. Your Matrix type is not copiable, thus you can't use Q_DECLARE_METATYPE on it. 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. QMetaType::type () returns the same ID as qMetaTypeId (), but does a lookup at runtime based on the name of the type. So in your case you need to declare. Firstly, you shouldn't need to use Q_DECLARE_METATYPE (or qRegisterMetaType) with the enum at all, this is handled by the moc. int videoSourceMetaTypeId = qRegisterMetaType< VideoSource > ();Declare new types with Q_DECLARE_METATYPE() to make them available to QVariant and other template-based functions. Since Qt 5. 0. Read and abide by the Qt Code of Conduct. This article will. After googling this, I found this correspondence, which was only available through a third party archival site as google. By convention, these files are given a . 该类型必须有公有的 构造、析构、复制构造 函数. qRegisterMetaType vs. Read and abide by the Qt Code of Conduct. ), or any other callable, cannot declare a type for use outside of the call site. Any class or struct that has a public default constructor, a public copy constructor, and a. Some structure need to be registered to be queued in asynchronous signals using qRegisterMetaType<T>(name), such as signal which passes QVector<int>. QMetaType registerNormalizedTypedef normalizedTypeName, type: metaType ); return. 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. Connect and share knowledge within a single location that is structured and easy to search. The ENUM type. Q_DECLARE_METATYPE (std::string) Quoting Qt Doc. 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. 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. This now makes it possible for Message values to be stored in QVariant objects and retrieved later. Compares this QVariant with v and returns true if they are equal;. 1. Using the qRegisterMetaType () function The Q_DECLARE_METATYPE () macro is the preferred way to declare a variable in Qt. " 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. qt. I read on documentation that Q_DECLARE_METATYPE makes available type to QVariant, for example (I got it from documentation): @ struct MyStruct { int i;. QAbstractSocket::SocketState is not a registered metatype, so for queued connections, you will have to register it with Q_REGISTER_METATYPE() and qRegisterMetaType(). cpp. The. What worries me is that. 3 Answers Sorted by: 13 "qRegisterMetaType" is a function. Here’s the list of what changed: QVariant used to forward isNull () calls to its contained type – but only for a limited set of Qt’s own types. Q_DECLARE_METATYPE only registers a type in meta type system. 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. 1. Enum has been moved from outside of the class to inside of it. Any class or struct that has a public default constructor, a public copy. To call qRegisterMetaType (), you still need to use Q_DECLARE_METATYPE (). 1）引入头文件：#include<QMetaType>. QML_DECLARE_TYPE. It associates a type name to a type so that it can be created and destructed dynamically at run-time. [override virtual] bool QLocalSocket:: waitForBytesWritten (int msecs = 30000) Reimplements:. J 1 Reply Last reply Reply Quote 0. Thanks for the suggestion. 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. 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. See also state() and Creating Custom Qt Types. As said in int qRegisterMetaType () documentation: To use the type T in QVariant, using Q_DECLARE_METATYPE () is sufficient. Q_DECLARE_METATYPE. Note that you are technically lying to the meta type system. 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(). 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. 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. 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. If you want both, then register both. until today. I'm confused by this error, as the documentation states (emphasis mine): Returns the meta type id of type T at compile time. This function was introduced in 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. Unsure if my idea would work, I created a DataPoint class marked with Q_GADGET with three properties defined using Q_PROPERTY. Re: Qt warning of type conversion already registered Originally. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. Without this reference, it compiles just fine. // But the split allows to. I guess it's the qRegisterMetaType () call itself that's missing. 12. Note that for enum types, you no not even need to call qRegisterMetaType () in these cases. Hello Ladies and Gentlemen. There's also no need for that typedef, it only makes the code less readable. Then you should register your object to use it with QML. I simplified the code quite a bit and the problem went away. Per Qt documentation: To use the type T in QVariant, using Q_DECLARE_METATYPE () is sufficient. 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. There's no need to call qRegisterMetaType that many times, once is enough. and Q_DECLARE_METATYPE uses qRegisterMetaType() internally. Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. ", which suggests it is only for classes and structs. 1 Answer. Connect and share knowledge within a single location that is structured and easy to search. 1. From the docs: int qRegisterMetaType ( const char * typeName ) Registers the type name typeName to the type T. QLocalSocket. However Q_DECLARE_METATYPE () is a bit more complicated. With Q_DECLARE_METATYPE and without qRegisterMetaType: No warning, slot is called With Q_DECLARE_METATYPE and with qRegisterMetaType: No warning, slot is called. +50. That's probably there, as qRegisterMetaType () wouldn't compile otherwise. 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. 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. Note: This function is thread-safe. That class receives a list of variants (wrapping various data) and converts those variants into a binary stream using QDataStream >. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug. So in your case you need to declare. struct StandardData { int EmpId; QString Name; }; Q_DECLARE_METATYPE (StandardData) Additionally, you might need to call qRegisterMetaType. That always worked in Qt4, but in Qt5 I get the following error: @error: specializing member ‘::qRegisterMetaType<Subclass>’ requires ‘template<>’ syntax@. 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. See also. Share Improve this answer Follow answered Jul 23, 2014 at 15:37. 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. rep file extension, short for Replica. To use the type T in queued signal and slot connections, qRegisterMetaType () must be called before the first connection is established. 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. h" class Context : public QObject { Q_OBJECT Q_PROPERTY (MyGadget* gadget READ gadget CONSTANT) public: explicit Context () : QObject {nullptr} { } MyGadget* gadget () { return &_gadget; } private. This object can then be passed from QML to C++ via. I need to call the Q_DECLARE_METATYPE() to pass the smart pointer. What is the point of emitting a QSharedPointer? The worker thread reads the files computes the data allocates and fills the memory with data, wraps it in QSharedPointer and passes it to the mainThread, which is used for plotting. Q_DECLARE_METATYPE, as pointed out by @SingerOfTheFall, would register template based type into QVariant (so it can be retrieved using qvariant_cast<T>()). First of all you need to declare your custom object for Qt metatype system. uint64; If this is your first visit, be sure to check out the FAQ by clicking the link above. cpp. goocreations 12 Mar 2013, 07:22. qRegisterMetaType vs. The reasoning is found in the discussion on Identity vs Value on the Qt Object Model page. container. The "traditional" way of doing this is to convert each element to a QVariant, and pass collection as a QVariantList. Qt Code: Switch view. Any class or struct that has a public constructor, a public copy constructor, and a public destructor can be registered. qRegisterMetaType is also called in the class constructor. @Wieland Thanks. An alternative would be to wrap shared_ptr<int> in your own class and implement comparison the way you want. Make a typedef for QSharedPointer<UserDataType>, and use both Q_DECLARE_METATYPE as well as qRegisterMetaType () to register it for use. QMetaType::type () is a bit slower, but compilation succeeds if a type is not registered. QtCore. qRegisterMetaType<Subclass> ("Subclass") also doesn't work. Please note that I do not use Q_DECLARE_METATYPE on purpose because I don't actually need its features (QVariant expansion) right now. To start viewing messages, select the forum that you want to visit from the selection below. Any class or struct that has a public default constructor, a public copy. This version of the function is to register alias types. QVariantList MyClass::getFooCollection (void) const { QVariantList list; for (const auto& l: fooCollection_) { list. private: AnotherQGadgetClass test_; } Q_DECLARE_METATYPE(QGadgetClass) I am trying to access Q_GADGET from QML classic way like accessing a Q_OBJECT , but the setters are not called. Reply Quote. 8. 23k 10 10 gold. ) I have defined MyStruct in an accessible header file: myheader. 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. the type name must be specified without the class, as in. The macro will register your variable with the Qt Meta-Object System, which will allow you to. To start viewing messages, select the forum that you want to visit from the selection below. Q_DECLARE_METATYPE (T) requires the type T to be default-constructable, copiable and destructable. Call qRegisterMetaType() to make type available to non-template based functions, such as the queued signal and slot connections. Using the macro directly turned out to be impossible. 总之，有时候，我们多么希望信号能发送自定义数据类型。. Re: How to use Q_DECLARE_METATYPE. I my real world application Context holds a large number of physical quantities (masses, forces, velocities,. I believe this is related to the fact that. Well, I certainly overplayed this particular point, but the statement I believe is valid in principle. If you only want to store pointer to Foo with the metatype system, then use qRegisterMetaType<Foo *> ();. 2 Answers. [override virtual] bool QAbstractSocket:: waitForBytesWritten (int msecs = 30000) Reimplements: QIODevice::waitForBytesWritten(int. There is no contradiction, because you can't register QObject descendants with Q_DECLARE_METATYPE. You could try using registerConverter () to allow implicit conversion of the shared_ptr<int> to a regular int, and compare them that way. ) 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. 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. Using Q_ENUM () allows you to retrieve at run-time the name of an enum value: Q_GADGET makes a class member, staticMetaObject, available. Is your Q_DECLARE_METATYPE in a header file or an implementation file? Incidentally, there is a mistake in TreeItem. Hello, Can someone tell me about how to register a metatype in pyqt5. 0 and have problems registering my own class as a QMetaType. This requires the exchanged data to be of a type that is recognizable by the engine. c:55 This looks like some loader initialization mismatch, check debug vs release builds of your application and libraries that are used. The object it returns should also be a member of the factory class. See also. struct Matrix { double data [4] [4]; }; Ideally you should be using eigen3. 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. The class is used as a helper to marshall types in QVariant and in queued signals and slots connections. See the Qt D-Bus Type System page for more information on the type system. Q_GADGET makes a class member, staticMetaObject, available. 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. As a workaround, I'm using QVariantMap instead of std::map. Q_DECLARE_METATYPE ( blabla* ) Also qRegisterMetaType<T> () is only required for sending your object through queued signal/slot connections. 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. Constantin. Note: it's also safe to call qRegisterMetaType () multiple times. This function is typically used together with construct () to perform low-level management of the memory used by a type. 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: This now makes it possible for Message values to be stored in QVariant objects and retrieved later. It is not safe to make a QObject's copy constructor public. Also, this Q_DECLARE_METATYPE(SharedTestClass) shouldn't be needed. I haven't used that module yet but one thing you should do is remove the string argument from your qRegisterMetaType calls. 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. 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. 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. A separate point for your own benefit. 幸哉~ Qt是支持自定义信号，且自定义信号可以发送自定义数据类型的对象。. Follow answered Jun 5, 2009 at 15:14. 4. See QMetaType docs for more information. cpp. You may have to register before you can post: click the register link above to proceed. However, I cannot figure out how to verify that the included parameter is FACE_UP or FACE_DOWN. no unexpected garbage. Now, in your registerTypes function, it should be registered like this: qRegisterMetaType<AccReal > ("data::AccReal"); In other words, the typeName string must match exactly the type of the signal argument as it is written there. Also you may need to use qRegisterMetaType function. qRegisterMetaType 必须使用该函数的两种情况. So you can call it from your constructor. In. When I try to simply connect signalslot with such QVector as argument programm tells during run that this metatype should be registered (though QVector, QSharedPointer and class inherited from QObject should be registered automatically. 如果是指针类型他需要有完整的定义。使用Q_DECLARE_OPAQUE_POINTER()去注册指针用于转发数据类型。 使用Q_DECLARE_METATYPE()可以让这个数据类型T放到QVariant里面。如果想以队列的方式让T使用信号与槽，当第一次连接的时候就要调用qRegisterMetaType<T>()。Detailed Description. Q_DECLARE_METATYPE(MyClass*); That's how Qt handles it with QObject and QWidget. The ones I am registering for are mostly structs for storing data and just a few simple classes. Teams. Any class or struct that has a public default constructor, a public copy constructor, and a public destructor can be registered. So, whatever Q_DECLARE_METATYPE is doing cannot be done by writing a function call. in a header file and call @qRegisterMetaType<std::unique_ptr<Thing>> ();@ before your signal and slots are used. However, as you need the type to be. 14. QMetaType. h. jsulm Lifetime Qt Champion @shivaVMC last edited by . D-Bus offers an extensible type system, based on a few primitive types and associations of them. You may have to register before you can post: click the register link above to proceed. That said, your stack trace is really strange: _dl_debug_initialize (ldbase=4294967292, ns=1095236752) at dl-debug.