struct package_manager { static constexpr auto package_name = "com. . Create ("Your Type"); It is not perfect but satisfied my requirement. The object it returns should also be a member of the factory class. hpp header in every Rust module that needs it. The QObject class provides a base class for objects that can take advantage of the meta-object system. One of the strengths of QML and C++ integration is the ability to implement UIs in QML separate from the C++ logic and dataset backend, and this fails if the C++ side starts manipulating QML directly. When I create a class in C++, I can register it for QML and can create view for it. The set of QML object-type attribute types is as follows: the id attribute. Creating a Client and. cpp then needs just this simple line outside of any function: EDIT: Sometimes this code makes the application to crash in debug mode. You also need to make adjustments in the build system. This QML file looks like this: import QtQuick 2. // An interface is not a QObject itself but is typically casted to one. There are several methods to modify a property of a QML element from python/C++, and each has its advantages and disadvantages. Each two adjacent elements in this list are intended to be connected together by the shortest line segment of constant bearing passing through both elements. For example, the following works: @. Returns the file path where a Local Storage database with the identifier databaseName is (or would be) located. The solution is to always work on Q_OBJECT s with pointers. 10以降のQML定義の列挙型もサポートしています。 air-dexによるC ++ベースの回答の代替として、QMLを使用して列挙型を作成できるようになりました。在c++中添加priorityEnum，以便在qml中使用. If Button. Unable to make qmlRegisterType work. The console. This function was introduced in Qt 5. Creating a Client and. In all other cases an invalid. 0//QML module not found (minimodel. Provide details and share your research! But avoid. A multimedia offloading software with a few tricks up its sleeve! - OffloadBuddy/main. QNetworkAccessManager is used for all network access by QML. One of the core features of QML is that it enables QML object types to be easily defined in a lightweight manner through QML documents to suit the needs of individual QML applications. W provides methods th. The Q_OBJECT macro. 0. New Global Functions. index: qt-creator/qt-creator. git. The path is defined by an ordered list of QGeoCoordinate objects. 15. These extensions allow custom QML types to be made available to the QML engine. This now makes it possible for Message values to be stored in QVariant objects and retrieved later. Select Assign, and then select OK . git. Meta type. To write a QML extension plugin: Subclass QQmlEngineExtensionPlugin and use the Q_PLUGIN_METADATA (). [since 5. Foo { id: foo} and can call your methods from elsewhere. Signals and slots are made possible by Qt's meta-object system. 0 \\import the main Qt QML module import "folderName" \\import the contents of the folder import "script. Q_INVOKABLE bool startBackUp(SomeEnum i); The Enum is definied in *. The QML engine provides built-in support for a large number. Normally, the QMetaObject is built at compile time from a C++ file generated by moc, Qt's meta object compiler. It applies QML, JavaScript and asset changes instantly on every connected device, immediately after saving. 6. Extending QML - Adding Types Example. The meta-object system is based on three things: The QObject class provides a base class for objects that can take advantage of the meta-object system. If we use QML_ELEMENT on the C++ side and want cmake to actually register the type, we need to add the sources to the SOURCES argument of qt_add_qml_module (). Commit 4772476 by @sztomi rightfully imports qml_register_enum in the prelude, but qml_register_enum only gets generated on Qt 5. QML doesn't recognise enums registered in a separate namespace. The QML engine can instantiate any Qt C++ construct such as properties, functions, and data models into the QML context allowing the constructs to be accessible from within QML. C++ and QML approach. The purpose of the wrapper classes is to separate the scripting interface from the actual class because I might not want to expose all of the signals and slots of the class. There were just a couple things wrong, related specifically to QML: The context properties must be set before the engine loads the qml file. name> QML_IMPORT_MAJOR_VERSION = <version>. For a given object instance, the READ method of a constant property must return the same value every time it is called. You can wrap the enum in a class which derives from QObject (and that you expose to QML): style. 12. 5 import QtQuick. Member Function Documentation QQmlEngine:: QQmlEngine (QObject *parent = nullptr) Create a new QQmlEngine with the given parent. 60 FPS means that there is approximately 16 milliseconds between each frame in which processing can be done, which includes the processing required to upload the draw primitives to the. Method 1: Passing the root object. As an application developer, you must strive to allow the rendering engine to achieve a consistent 60 frames-per-second refresh rate. This enables C++ data and functions. You can connect a signal to a slot with connect () and destroy the connection with disconnect (). Toggle table of contents sidebar. For example, I am creating a slightly modified SplitView from C++ like this: QQmlEngine* engine = QtQml::qmlEngine ( this ); QQmlComponent splitComp ( engine, QUrl ( "qrc:/qml/Sy. def checkConnectArgs (signal, method). Using a scene graph for graphics rather than the traditional imperative painting systems (QPainter or similar), means the scene to be rendered can be retained between frames and the complete set of primitives to render is known before rendering starts. @JKSH said in Undefined reference to staticMetaObject: you can force moc to run by running qmake. In your main file, register the class so QML can find it: qmlRegisterType<Foo> ("MyFoo", 1, 0, "Foo"); Import your C++ class in your QML file import MyFoo 1. The file format of the media. In order to be able to use a type in a signal or method parameter, or as a property type, the type need to implement. Qt adds these features to C++: a very powerful mechanism for seamless object communication called signals and slots. cpp. QML can easily be extended with functionality defined in C++ code. To activate it, execute the following code as early as possible in main(): fn main() { qmetaobject::log::init_qt_to_rust(); // don't forget to set up env_logger or any other logging backend. This requires the exchanged data to be of a type that is recognizable by the engine. Here You need create this class object before use setContextProperty (). 要访问 qml中 的枚举值，必须使用以下宏将其提供. 说明qmlRegisterUncreatableType ()将用QML类型系统将c++类类型 (派生自QObject)注册为非实例化类型。. Note that CMake will, by default, automatically generate the qmldir file. 13. class PyQml (QObject): def __init__ (self, parent=None): super (). About. The Qt solution works with any standard C++ compiler on every platform Qt supports. In the first post we've set up the environment. QObject is the heart of the Qt Object Model. Note that the value returned by this function is the QDebug object itself, though this is often obtained by calling the maybeSpace() member function of QDebug that pads out the stream with space characters to make it more readable. hpp namespace application { Q_NAMESPACE enum class BookOperationStatus { Success,. @bogong said in Pass object like property into QML Component. The frame rate of the media's video stream. opMode. 1 Answer. Yes i do. See the docs on Component element. This tool is called qmake. First, right-click the C++ “Sources” folder of your project in Qt Creator, select “Add New…” and choose the “C++ Class” template in the C++ section: 3. It is not possible however to modify the global object, so true global JS-functions are not. I have got a QQuickView which has loaded a qml file like the following. The c++ (cpp) qmlregisteruncreatablemetaobject example is extracted from the most popular open source projects, you can refer to the following example for usage. self. int QQmlPropertyMap:: size const. Type is not registered, please use the Q_DECLARE_METATYPE macro to make it known to Qt's meta-object system. 2 there is, for the first time, a comprehensive build system API that allows you to specify a QML module as a complete, encapsulated unit. Contactindex: qt-creator/qt-creator. Qt 5 - qmlRegisterType gives "module is not installed". I create a new Qt Quick 2 project and add the following contents: #Add more folders to ship with the application, here folder_01. 5 import QtQuick. The solution is to always work on Q_OBJECTs with pointers. class MyQmlType : public QObject. class Element : public QObject { Q_OBJECT private: QString type; QLinkedList<Element*> child; public: explicit Element (QString type, QLinkedList<Element*> child); virtual ~Element ();. Among other things, meta-object code is required for the signals and slots. 6 answers. h - pass around objects of this type between C++ and QML. Note that CMake will, by default, automatically generate the qmldir file. This enables C++ data and functions. package"; static constexpr auto package_version_major = 0; static constexpr auto package_version_minor = 1; } Then create your Qt Object, and expose the properties to the QML engine: One of the strengths of QML and C++ integration is the ability to implement UIs in QML separate from the C++ logic and dataset backend, and this fails if the C++ side starts manipulating QML directly. QQmlApplicationEngine::QQmlApplicationEngine (const QString &filePath、 QObject *parent= nullptr) 新しい QQmlApplicationEngine を作成し、指定された場所に QML ファイルをロードします filePath、これはローカル ファイル パスである必要があります。. controls 2. Getting The IP Address. ** accordance with the commercial license agreement provided with the. Normally, the QMetaObject is built at compile time from a C++ file generated by moc, Qt's meta object compiler. So every time I need to create one more class, copy already implemented, change class name, change strings in registration method and add necessary enums. The moc tool reads a C++ header file. Attributes in Object Declarations. Detailed Description. I'm currently practicing the QML and I need to pass several data from the C++ to the Qml. cpp file (or wherever you have access to QML engine) using QQmlContext::setContextProperty (const QString &name, QObject *value) method on the engine’s root context. First, we will create a menu containing buttons which will eventually perform different actions. The set of QML object-type attribute types is as follows: the id attribute. index: qt-creator/qt-creator. The answer is "yes," it works. Qt provides this, by combining the speed of C++ with the flexibility of the Qt Object Model. QQmlEngineExtensionPlugin is a plugin interface that makes it possible to create QML extensions that can be loaded dynamically into QML applications. I was wondering about the behaviour of the registered type with the qml engine. qqmlengine. The bit rate of the media's audio stream in bits per second. A signal is also a method. Take a look at this article: Dynamic Object Management in QML and on this part especially: Note that. Qt's meta-object system provides the signals and slots mechanism for inter-object communication, run-time type information, and the dynamic property system. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. Hey, I am trying to return an enum from my C++ code, my enum is defined in a namespace, and looks like this: // book_operation_status. For qmake, add CONFIG += qmltypes, a QML_IMPORT_NAME, and a QML_IMPORT_MAJOR_VERSION to your project file. property attributes. If it represents a type, it returns QMetaType::Int. For more information about setting up a secure CoAP server, see Setting Up a Secure CoAP Server. The Q_OBJECT macro inside the private section. Next time you post code make sure it is runnable: Create a new test project. Hey, I am trying to return an enum from my C++ code, my enum is defined in a namespace, and looks like this: // book_operation_status. not possible in the way @Subbu is building his program. The qRegisterMetaType function essentially allows a typedef or alias to be assigned to a QVariant. The Object and List Property Types example shows how to add object and list properties in QML. mohabouje. ) by:. <2> The class has a pointer to another QObject derived class and the pointer is accessible to QML via Q_PROPERTY. cpp" for registering C++ to QML. Defining QML Types from C++. QApplication app (argc, argv); QQmlApplicationEngine engine; engine. Instead of using QML_ELEMENT and CONFIG += qmltypes, which is brand new from Qt 5. Each two adjacent elements in the path are intended to be connected together by the shortest line segment of constant bearing passing through both elements. . find_package (Qt6 REQUIRED COMPONENTS VirtualKeyboard) target_link_libraries (mytarget PRIVATE Qt6::VirtualKeyboard) qmake: QT += virtualkeyboard. git. There are downsides to this approach: You always need to keep your type registrations in sync with the actual types. You can't actually use Q_ENUM with Q_NAMESPACE, but you can use Q_ENUM_NS instead. For more information about setting up a secure CoAP server, see Setting Up a Secure CoAP Server. New Classes. For more information on accessing QML objects. I have a question about namespace-scoped QFlags definitions. I had the exact same issue. 452. The QMetaObject is a data structure which contains all the information about a class deriving from QObject (or Q_GADGET) so the Qt runtime can connect signals with slots, or read and write properties. 1 which doesn't provide. @J-Hilk said in Slot not invoked when sending signal with enum values:. I use both concepts. The Singleton design pattern is a useful software design pattern for Qt/QML applications that need access to certain services or logic-heavy backend components. This has been changed, and isNull () now only returns true if the QVariant is empty or contains a nullptr. The QtObject type is a non-visual element which contains only the objectName property. def disconnect (sender, signal_index, receiver, method_index. Create a project folder for the app, in our example we will call it: clock. The QObject. I've found some examples of qmlRegisterType on the internet but just can't make it work. } But is it possible to create a QML component from a string? Detailed Description. TypeError: Cannot access enum value 'imgLoadAnim6' of 'AppEnumsNs', enum values need to start with an uppercase letter. The Q_OBJECT macro inside the private section of the class declaration is used to enable meta-object features, such as dynamic properties, signals, and slots. index: qt-creator/qt-creator. mzimmers @mzimmers 9 days ago. hpp namespace application { Q_NAMESPACE enum class BookOperationStatus { Success,. opMode. property attributes. C++ and QML approach. API Design Principles. This looks like the Q_NAMESPACE macro isn’t recognized by autogen as a trigger for “please moc this” (as your subject seems to find). The aim of my "project" is to display data which were red from an external JSON file. This has the same purpose as the C++ qmlRegisterSingletonType function but uses qmlRegisterSingletonInstance, which was introduced in Qt 5. The Meta-Object System. Getting The IP Address. It's purpose is to connect to a database, as shown in following code: #ifndef UESQLDATABASE_H #define2. k_administration. 12. Here is my SimpleMainWindow. property attributes. Good to know this. createQmlObject (string) It is possible to create QML components from code via Component {. It will catch more errors during compilation time. QObject is the base class for all Qt classes, Q_OBJECT macro is used to enable meta-object features in classes and finally moc is a preprocessor that changes Q_OBJECT macro instances to C++ source code to enable. Simple example: ApplicationWindow { id: root visible: true width: 400 height: 680 Item { id: item function a() { console. Select Tools > Options > Environment > Keyboard. class MyClass : public QObject { Q_OBJECT Q_PROPERTY(Priority priority READ priority WRITE setPriority NOTIFY priorityChanged) public: MyClass(QObject *parent = nullptr); ~MyClass(); enum Priority { High, Low, VeryHigh, VeryLow }; Q_ENUM(Priority) void setPriority(Priority priority) { m_priority =. index: qt-creator/qt-creator. qmlRegisterUncreatableMetaObject(Strings::staticMetaObject, "MyConstants", 1, 0, "Strings", "Not Instantiable!" ); this always results in. git. 0. The Q_OBJECT macro inside the private. and another folder with the obj files. . You must pass a name under which the object will be accessible and the pointer to a QML object. Such an approach also makes changing the QML UI difficult without affecting its C++ counterpart. Connected to the property system is an additional macro, Q_CLASSINFO (), that can be used to attach additional name -- value pairs to a class's meta-object, for example: Q_CLASSINFO("Version","3. It also declares an object hierarchy that will be instantiated should an instance of that newly defined type be created. Method 1: Passing the root object. I create a new Qt Quick 2 project and add the following contents: This is. You can use setContextProperty to make a variable globally available in QML: engine. index: qt-creator/qt-creator. I have problems receiving the signal mySignal with the correct enum type in qml. first ())); Now you can access the root object in QML using rootObject and pass it to MyCustomType during construction. 所以我们不能在 qml 文件 中 为类创建对象，但是我们可以在 qml 文件 中 使用属性ans 枚举类型 属于这个类。. . 2. Code example to test dynamic meta objects in Qt 5. Until then you have to use qt5_wrap_cpp(moc_file ns. The QObject class provides a base class for objects that can take advantage of the meta-object system. So instead of looking for a QQuickWidget, access the engines rootContext - replace: QQuickWidget *myObject = static_cast<QQuickWidget*> (engine. __init__ (parent) # Initialise the value of the properties. ERROR: undefined reference to `Exception::staticMetaObject'. The presence of the CONSTANT attribute indicates that the property value is constant. It can be useful to create a QtObject if you need an extremely. first ()); QQmlContext *context = myObject->rootContext (); context. git. Stack Overflow is leveraging AI to summarize the most relevant questions and answers from the community, with the option to ask follow-up questions in a conversational format. qml as shown below. 8] int qmlRegisterUncreatableMetaObject (const QMetaObject &staticMetaObject, const char *uri, int versionMajor, int versionMinor, const char *qmlName, const QString. Next, we declare a custom QObject, just like in the overview, but this time it derives from QQuickItem. Such an approach also makes changing the QML UI difficult without affecting its C++ counterpart. EnumValue, while the C++ enum values must be adressed just with EnumType. The standard Qt Quick module provides various types like Rectangle, Text and Image for building a QML application; beyond these, you can easily define your own. Hi All, Is there a way to expose multiple enums from one class to QML, and keep the namespaces. As described in the introduction, the QObject is what enables many of Qt's core functions such as signals and slots. [signal] void QQmlEngine:: exit (int retCode) This signal is emitted when the QML loaded by the engine would like to exit from the event loop with the specified return code retCode. invoke(this); And let Qt handles the call to activate(). source = qml/testlib folder_01. cpp. Register a Type. In simplest terms (credit to this post ): // header file of your choice namespace EquipmentNS { Q_NAMESPACE enum Category {. Running the Example. My workround was to explicitly cast the enum values to int when passing them onto a function requiring a QVariant type, in my case. . 0") Like other meta-data, class information is accessible at run-time through the meta-object; see QMetaObject::classInfo () for details. I've got a C++ class (class A) from a library that I want to interface with QML. For instance I have enum from thirdparty library: namespace Lib { enum class Foo { Bar, Baz }; }; I have tried use next wrapper namespace Qml { Q_NAMESPACE using Foo = Lib::Foo. import QtQuick 1. In simplest terms (credit to this post): // header file of your choice namespace EquipmentNS { Q_NAMESPACE enum Ca. Controls 1. Now I want to get the class name from this object. ) { qRegisterMetaType<EnumerationStorage::A> ("A"); qmlRegisterUncreatableMetaObject (EnumerationStorage::staticMetaObject,. Only here I get the errror message: Q_INVOKABLE bool startBackUp(SomeEnum i); ``` //Error: Unknown method parameter type: MyNamespace. One of Qt's most reputed merits is its consistent, easy-to-learn, powerful API. The associated property change signal handler generated by the QML engine will always take the form on<Property>Changed, regardless of the name of the related C++ signal, so it is recommended that the signal name follows. See also isEmpty() and count(). An object declaration in a QML document defines a new type. I had the exact same issue. Then instantiate your class object and expose it in main. The QMetaType class manages named types in the meta-object system. Detailed Description. If you're using qmake, create a qmldir file to describe the plugin. This is the third installment in the series of blog posts on how to adjust your QML application to take the maximum advantage of qmlsc. I have defined a namespace with enums in C++ to use both in C++ and QML code. cppThe c++ (cpp) qmlregisteruncreatablemetaobject example is extracted from the most popular open source projects, you can refer to the following example for usage. 0" on the QML side. Then you can obtain the IP address with the following command:Problem I'm trying to register a namespace in QML from a shared library, but the compilation fails with an unresolved external symbol error: failed (exit code 1120) with the following output: main. CryptoA tag already exists with the provided branch name. [virtual protected] QVariant QQmlPropertyMap:: updateValue (const QString &key, const QVariant &input) Returns the new value to be stored for the key key. miniModel 1. You can declare properties of an uncreatable type in a C++ type declaration only. Read and abide by the Qt Code of Conduct. _name = '' self. Graphical user interface programming is a domain that requires both runtime efficiency and a high level of flexibility. If it finds one or more class declarations that contain the Q_OBJECT macro, it produces a C++ source file containing the meta-object code for those classes. To run the example application, you first need to set up a secure CoAP server. qml: Type HPACIcons unavailable qrc: /qml/IconFont / IconFont. 0. If instead the enum is placed into a QObject derived class and the class type is registered in the same way using qmlRegisterType () then the QML editor provides autocomplete for the enum values, but. This attribute was introduced in Qt 6. QML Modules. The problem is that the staticMetaObject associated to your class is not initialized at the moment the macro invokes the call to qmlRegisterType. It is possible to create QML components from files using Qt. I want to add just one command [qmlRegisterType("MyLib", 1, 0, "QmlConnector");] to "main. Example: {. For more information on accessing QML objects. In the Show commands containing field, enter Help. Contribute to qt-creator/qt-creator development by creating an account on GitHub. And also with Integer. The central feature in this model is a very powerful mechanism for seamless object communication called signals and slots. The documenation of this macro gives us a good hint. hpp : #ifndef STYLE_HPP #define STYLE_HPP #include <QtGlobal> #if QT_VERSION < QT_VERSION_CHECK(5,0,0) // Qt 4 #include <QDeclarativeEngine> #else // Qt 5 #include <QQmlEngine> #endif // Required derivation from QObject class StyleClass : public QObject { Q_OBJECT public: // Default constructor. . Controls 2. void Component:: addAutoDependOn (const QString & newDependOn) Adds the component specified by newDependOn to the automatic depend-on list. If it finds one or more class declarations that contain the Q_OBJECT macro, it produces a C++ source file containing the meta-object code for those classes. 10. These extensions allow custom QML types to be made available to the QML engine. onClicked: { listProperty (ItemID) //or with this to list self properties listProperty (this) }In each QMetaObject, the slots, signals and other invokable methods of that object are given an index, starting from 0. git. ui", 1, 0, "GameWidget"); Did anyone find a solution?Hey, I've created a simple QAbstractItemModel subtype to use in my TreeView: When trying to instantiate it in qml, it tells me Element is not creatable. See Q_INVOKABLE. Note: Since all expressions evaluated in QML are evaluated in a particular context, if the context is. Sorted by: 2. I'd try to encapsulate your DataHandler* in QVariant and make the property of type QVariant. 0 in QML. We have been recently talking about the QML to C++ compilation, but this was mostly describing the process of compiling your JavaScript code. An import statement allows clients to tell the engine which modules, JavaScript resources and component directories are used within a QML document. first ())); Now you can access the root object in QML using rootObject and pass it to MyCustomType during construction. 15 (latest when writing this), and not supported at this time with CMake, use the good old qmlRegisterType from C++: #include "YouCustomCppClass. It works only in this case int qmlTypeId = qRegisterMetaType<namespace::MenuModel*> ("MenuModel*"); You return a pointer in the property, so Qt Meta Object system needs to know about it. An object declaration in a QML document defines a new type. So you could include this file in your qml files and use this array. These extensions allow custom QML types to be made available to the QML engine. Viewed 307 times. The QML engine uses the QProperty macro to register the cpp method setMode as the symbol to use when setting the property -- it doesn't expose the method itself. property attributes. c++ qt qml qtquick2. qqmlengine. 18th November 2016, 09:38 #7. This attribute was introduced in Qt 6. Contactindex: qt-creator/qt-creator. The QML engine provides built-in support for a. This maintains their identity, and. index: qt-creator/qt-creator. rootObjects (). 1. Registers a QML singleton object. Data Type Conversion Between QML and C++. Member Function Documentation QQmlEngine:: QQmlEngine (QObject *parent = nullptr) Create a new QQmlEngine with the given parent. . 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. } So far the simplest and cleanest solution I found is to make a C++ macro like this: #define QML_REGISTER (a) static int unused_val = qmlRegisterType<a> ("my_uri", 1, 0, #a) MyClass. Scene Graph Item Qt Quick 2 makes use of dedicated scene graph for its rendering. The QObject class provides a base class for objects that can take advantage of the meta-object system. The set of QML object-type attribute types is as follows: the id attribute. 0, 454. QString QQmlEngine:: offlineStorageDatabaseFilePath (const QString & databaseName) const. Contribute to dliess/Push2Control development by creating an account on GitHub. To run the example application, you first need to set up a secure CoAP server. You can wrap the enum in a class which derives from QObject (and that you expose to QML): style. source = qml/testlib folder_01. 0. C++ (Cpp) qmlRegisterUncreatableMetaObject - 2 examples found. cpp at master · jslauthor/glitchdrawHi everyone. This is the project file (extension . New Member Functions. qmlRegisterUncreatableMetaObject(MyNamespace:: staticMetaObject, "io. One of the strengths of QML and C++ integration is the ability to implement UIs in QML separate from the C++ logic and dataset backend, and this fails if the C++ side starts manipulating QML directly. 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. Window 2. 10. cpp. . The QFlags<Enum> class is a template class, where Enum is an enum type. b",1,0,"c"); and import a. For more information on accessing QML objects. The c++ (cpp) qmlregisteruncreatablemetaobject example is extracted from the most popular open source projects, you can refer to the following example for usage. Properties of type real, int, color, rect, point, size, and vector3d can all be animated. Now I want to get the class name from this object. The presence of the CONSTANT attribute indicates that the property value is constant. This requires the exchanged data to be of a type that is recognizable by the engine. See Defining QML Types from C++ for more information. Such an approach also makes changing the QML UI difficult without affecting its C++ counterpart. ,CodeAntenna技术文章技术问题代码片段及聚合This allows for registering structs that don't implement Default, mirroring C++'s QQmlEngine::qmlRegisterUncreatableType. Qt provides a sophisticated property system similar to the ones supplied by some compiler vendors. QMetaType::construct (), QMetaType::sizeOf (), and QMetaType::alignOf. How to retrieve a root object (the code below returns 0, rootContext()->findChild() also returns 0) from anywhere in a C++ code (a class method where the class is a registered QML type and the class component definition is a direct child of the root, see objectName) and add a generated QQuickItem at runtime? There is myclass registered.