QQmlEngine Class

See also QQmlComponent, QQmlContext, QML Global Object

This property holds the directory for storing offline user data

Returns the directory where SQL and other offline storage is placed.

The SQL databases created with openDatabaseSync() are stored here.

The default is QML/OfflineStorage in the platform-standard user application data directory.

Note that the path may not currently exist on the filesystem, so callers wanting to create new files at this location should create it first - see QDir::mkpath().

Access functions:

• offlineStoragePath() const

• void setOfflineStoragePath(const &dir)

Notifier signal:

• void offlineStoragePathChanged()

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Create a new QQmlEngine with the given parent.

Destroys the QQmlEngine.

Any QQmlContext's created on this engine will be invalidated, but not destroyed (unless they are parented to the QQmlEngine object).

See QJSEngine docs for details on cleaning up the JS engine.

Sets the provider to use for images requested via the image: url scheme, with host providerId. The QQmlEngine takes ownership of provider.

Image providers enable support for pixmap and threaded image requests. See the QQuickImageProvider documentation for details on implementing and using image providers.

All required image providers should be added to the engine before any QML sources files are loaded.

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Adds path as a directory where the engine searches for installed modules in a URL-based directory structure.

The path may be a local filesystem directory, a Qt Resource path (:/imports), a Qt Resource url (qrc:/imports) or a URL.

The path will be converted into canonical form before it is added to the import path list.

The newly added path will be first in the importPathList().

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Adds path as a directory where the engine searches for native plugins for imported modules (referenced in the qmldir file).

By default, the list contains only ., i.e. the engine searches in the directory of the qmldir file itself.

The newly added path will be first in the pluginPathList().

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Adds a urlInterceptor to be used when resolving URLs in QML. This also applies to URLs used for loading script files and QML types. The URL interceptors should not be modifed while the engine is loading files, or URL selection may be inconsistent. Multiple URL interceptors, when given, will be called in the order they were added for each URL.

QQmlEngine does not take ownership of the interceptor and won't delete it.

Return the base URL for this engine. The base URL is only used to resolve components when a relative URL is passed to the QQmlComponent constructor.

If a base URL has not been explicitly set, this method returns the application's current working directory.

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Clears the engine's internal component cache.

This function causes the property metadata of all components previously loaded by the engine to be destroyed. All previously loaded components and the property bindings for all extant objects created from those components will cease to function.

This function returns the engine to a state where it does not contain any loaded component data. This may be useful in order to reload a smaller subset of the previous component set, or to load a new version of a previously loaded component.

Once the component cache has been cleared, components must be loaded before any new objects can be created.

As a general rule of thumb, make sure that no objects created from QML components are alive when you clear the component cache.

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Clears all singletons the engine owns.

This function drops all singleton instances, deleting any QObjects owned by the engine among them. This is useful to make sure that no QML-created objects are left before calling clearComponentCache().

QML properties holding QObject-based singleton instances become null if the engine owns the singleton or retain their value if the engine doesn't own it. The singletons are not automatically re-created by accessing existing QML-created objects. Only when new components are instantiated, the singletons are re-created.

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Returns the QQmlContext for the object, or 0 if no context has been set.

When the QQmlEngine instantiates a QObject, the context is set automatically.

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Reimplements: QObject::event(QEvent *e).

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.

This function was introduced in Qt 5.8.

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Returns the image provider set for providerId if found; otherwise returns nullptr.

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Returns the list of directories where the engine searches for installed modules in a URL-based directory structure.

For example, if /opt/MyApp/lib/imports is in the path, then QML that imports com.mycompany.Feature will cause the QQmlEngine to look in /opt/MyApp/lib/imports/com/mycompany/Feature/ for the components provided by that module. A qmldir file is required for defining the type version mapping and possibly QML extensions plugins.

By default, the list contains the directory of the application executable, paths specified in the QML_IMPORT_PATH environment variable, and the builtin QmlImportsPath from QLibraryInfo.

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Returns the currently set incubation controller, or 0 if no controller has been set.

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Run the current URL interceptors on the given url of the given type and return the result.

Returns a common QNetworkAccessManager which can be used by any QML type instantiated by this engine.

If a QQmlNetworkAccessManagerFactory has been set and a QNetworkAccessManager has not yet been created, the QQmlNetworkAccessManagerFactory will be used to create the QNetworkAccessManager; otherwise the returned QNetworkAccessManager will have no proxy or cache set.

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Returns the current QQmlNetworkAccessManagerFactory.

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Returns the file path where a Local Storage database with the identifier databaseName is (or would be) located.

This function was introduced in Qt 5.9.

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Returns true if warning messages will be output to stderr in addition to being emitted by the warnings() signal, otherwise false.

The default value is true.

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Returns the list of directories where the engine searches for native plugins for imported modules (referenced in the qmldir file).

By default, the list contains only ., i.e. the engine searches in the directory of the qmldir file itself.

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This signal is emitted when the QML loaded by the engine would like to quit.

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Removes the image provider for providerId.

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Remove a urlInterceptor that was previously added using addUrlInterceptor. The URL interceptors should not be modifed while the engine is loading files, or URL selection may be inconsistent.

This does not delete the interceptor, but merely removes it from the engine. You can re-use it on the same or a different engine afterwards.

Refreshes all binding expressions that use strings marked for translation.

Call this function after you have installed a new translator with QCoreApplication::installTranslator, to ensure that your user-interface shows up-to-date translations.

This function was introduced in Qt 5.10.

Returns the engine's root context.

The root context is automatically created by the QQmlEngine. Data that should be available to all QML component instances instantiated by the engine should be put in the root context.

Additional data that should only be available to a subset of component instances should be added to sub-contexts parented to the root context.

Set the base URL for this engine to url.

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Sets the QQmlContext for the object to context. If the object already has a context, a warning is output, but the context is not changed.

When the QQmlEngine instantiates a QObject, the context is set automatically.

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Sets paths as the list of directories where the engine searches for installed modules in a URL-based directory structure.

By default, the list contains the directory of the application executable, paths specified in the QML_IMPORT_PATH environment variable, and the builtin QmlImportsPath from QLibraryInfo.

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Sets the engine's incubation controller. The engine can only have one active controller and it does not take ownership of it.

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Sets the factory to use for creating QNetworkAccessManager(s).

QNetworkAccessManager is used for all network access by QML. By implementing a factory it is possible to create custom QNetworkAccessManager with specialized caching, proxy and cookie support.

The factory must be set before executing the engine.

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Set whether warning messages will be output to stderr to enabled.

If enabled is true, any warning messages generated by QML will be output to stderr and emitted by the warnings() signal. If enabled is false, only the warnings() signal will be emitted. This allows applications to handle warning output themselves.

The default value is true.

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Sets the list of directories where the engine searches for native plugins for imported modules (referenced in the qmldir file) to paths.

By default, the list contains only ., i.e. the engine searches in the directory of the qmldir file itself.

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Returns the instance of a singleton type that was registered under qmlTypeId.

The template argument T may be either QJSValue or a pointer to a QObject-derived type and depends on how the singleton was registered. If no instance of T has been created yet, it is created now. If qmlTypeId does not represent a valid singleton type, either a default constructed QJSValue or a nullptr is returned.

QObject* example:

class MySingleton : public QObject {
    Q_OBJECT

    // Register as default constructed singleton.
    QML_ELEMENT
    QML_SINGLETON

    static int typeId;
    // ...
};

    MySingleton::typeId = qmlTypeId(...);

    // Retrieve as QObject*
    QQmlEngine engine;
    MySingleton* instance = engine.singletonInstance<MySingleton*>(MySingleton::typeId);

QJSValue example:

    // Register with QJSValue callback
    int typeId = qmlRegisterSingletonType(...);

    // Retrieve as QJSValue
    QQmlEngine engine;
    QJSValue instance = engine.singletonInstance<QJSValue>(typeId);

It is recommended to store the QML type id, e.g. as a static member in the singleton class. The lookup via qmlTypeId() is costly.

This function was introduced in Qt 5.12.

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Trims the engine's internal component cache.

This function causes the property metadata of any loaded components which are not currently in use to be destroyed.

A component is considered to be in use if there are any extant instances of the component itself, any instances of other components that use the component, or any objects instantiated by any of those components.

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Returns the list of currently active URL interceptors.

This signal is emitted when warnings messages are generated by QML.

Defines some special values that can be passed to the version arguments of qmlRegisterModuleImport() and qmlUnregisterModuleImport().

The form of this template function is:

template<typename T> QObject *qmlAttachedPropertiesObject(const QObject *attachee, bool create = true)

This returns the attached object instance that has been attached to the specified attachee by the attaching type T.

If create is true and type T is a valid attaching type, this creates and returns a new attached object instance.

Returns 0 if type T is not a valid attaching type, or if create is false and no attachment object instance has previously been created for attachee.

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Clears all stored type registrations, such as those produced with qmlRegisterType().

Do not call this function while a QQmlEngine exists or behavior will be undefined. Any existing QQmlEngines must be deleted before calling this function. This function only affects the application global cache. Delete the QQmlEngine to clear all cached data relating to that engine.

Returns the QQmlContext associated with object, if any. This is equivalent to QQmlEngine::contextForObject(object).

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Prints debug messages that include the file and line number for the specified QML object.

When QML types produce logging messages, it improves traceability if they include the QML file and line number on which the particular instance was instantiated.

To include the file and line number, an object must be passed. If the file and line number is not available for that instance (either it was not instantiated by the QML engine or location information is disabled), "unknown location" will be used instead. For example,

qmlDebug(object) << "Internal state: 42";

prints

QML MyCustomType (unknown location): Internal state: 42

This function was introduced in Qt 5.9.

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Returns the QQmlEngine associated with object, if any. This is equivalent to QQmlEngine::contextForObject(object)->engine(), but more efficient.

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Prints informational messages that include the file and line number for the specified QML object.

When QML types produce logging messages, it improves traceability if they include the QML file and line number on which the particular instance was instantiated.

To include the file and line number, an object must be passed. If the file and line number is not available for that instance (either it was not instantiated by the QML engine or location information is disabled), "unknown location" will be used instead.

For example,

qmlInfo(object) << tr("component property is a write-once property");

prints

QML MyCustomType (unknown location): component property is a write-once property

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This function protects a module from further modification. This can be used to prevent other plugins from injecting types into your module. It can also be a performance improvement, as it allows the engine to skip checking for the possibility of new types or plugins when this import is reached.

Once qmlProtectModule has been called, a QML engine will not search for a new qmldir file to load the module anymore. It will re-use any qmldir files it has loaded before, though. Therefore, types present at this point continue to work. Mind that different QML engines may load different modules. The module protection, however, is global and affects all engines. The overhead of locating qmldir files and loading plugins may be noticeable with slow file systems. Therefore, protecting a module once you are sure you won't need to load it anymore can be a good optimization. Mind also that the module lock not only affects plugins but also any other qmldir directives, like import or prefer, as well as any composite types or scripts declared in a qmldir file.

In addition, after this function is called, any attempt to register C++ types into this uri, major version combination will lead to a runtime error.

Returns true if the module with uri as a module identifier and majVersion as a major version number was found and locked, otherwise returns false. The module must contain exported types in order to be found.

This template function registers the C++ type in the QML system as an anonymous type. The resulting QML type does not have a name. Therefore, instances of this type cannot be created from the QML system. You can, however, access instances of the type when they are exposed as properties of other types.

Use this function when the type will not be referenced by name, specifically for C++ types that are used on the left-hand side of a property binding. To indicate to which module the type belongs use uri and versionMajor.

For example, consider the following two classes:

class Bar : public QObject
{
    Q_OBJECT
    Q_PROPERTY(QString baz READ baz WRITE setBaz NOTIFY bazChanged)

public:
    Bar() {}

    QString baz() const { return mBaz; }

    void setBaz(const QString &baz)
    {
        if (baz == mBaz)
            return;

        mBaz = baz;
        emit bazChanged();
    }

signals:
    void bazChanged();

private:
    QString mBaz;
};

class Foo : public QObject
{
    Q_OBJECT
    Q_PROPERTY(Bar *bar READ bar CONSTANT FINAL)

public:
    Foo() {}

    Bar *bar() { return &mBar; }

private:
    Bar mBar;
};

In QML, we assign a string to the baz property of bar:

Foo {
    bar.baz: "abc"
    Component.onCompleted: print(bar.baz)
}

For the QML engine to know that the Bar type has a baz property, we have to make Bar known:

qmlRegisterType<Foo>("App", 1, 0, "Foo");
qmlRegisterAnonymousType<Bar>("App", 1);

As the Foo type is instantiated in QML, it must be registered with the version of qmlRegisterType() that takes an element name.

Returns the QML type id.

This function was introduced in Qt 5.14.

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This template function registers the C++ type and its extension object in the QML system with the name qmlName in the library imported from uri having version number composed from versionMajor and versionMinor. Properties not available in the main type will be searched for in the extension object.

Returns the QML type id.

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This template function registers the C++ type and its extension in the QML system with the name qmlName in the library imported from uri having version number composed from versionMajor and versionMinor.

While the type has a name and a type, it cannot be created. An error message with the given reason is printed if the user attempts to create an instance of this type.

This is useful where the type is only intended for providing attached properties, enum values or an abstract base class with its extension.

Returns the QML type id.

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This function registers a module in a particular uri with a version specified in versionMajor and versionMinor.

This can be used to make a certain module version available, even if no types are registered for that version. This is particularly useful for keeping the versions of related modules in sync.

This function was introduced in Qt 5.9.

Registers an implicit import for module uri of major version moduleMajor.

This has the same effect as an import statement in a qmldir file: Whenever uri of version moduleMajor is imported, import of version importMajor. importMinor is automatically imported, too. If importMajor is QQmlModuleImportLatest the latest version available of that module is imported, and importMinor does not matter. If importMinor is QQmlModuleImportLatest the latest minor version of a importMajor is chosen. If importMajor is QQmlModuleImportAuto the version of import is version of uri being imported, and importMinor does not matter. If moduleMajor is QQmlModuleImportModuleAny the module import is applied for any major version of uri. For example, you may specify that whenever any version of MyModule is imported, the latest version of MyOtherModule should be imported. Then, the following call would be appropriate:

qmlRegisterModuleImport("MyModule", QQmlModuleImportModuleAny,
                        "MyOtherModule", QQmlModuleImportLatest);

Or, you may specify that whenever major version 5 of "MyModule" is imported, then version 3.14 of "MyOtherModule" should be imported:

qmlRegisterModuleImport("MyModule", 5, "MyOtherModule", 3, 14);

Finally, if you always want the same version of "MyOtherModule" to be imported whenever "MyModule" is imported, specify the following:

qmlRegisterModuleImport("MyModule", QQmlModuleImportModuleAny,
                        "MyOtherModule", QQmlModuleImportAuto);

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This template function registers the specified revision of a C++ type in the QML system with the library imported from uri having the version number composed from versionMajor and versionMinor.

Returns the QML type id.

template<typename T, int metaObjectRevision>
int qmlRegisterRevision(const char *uri, int versionMajor, int versionMinor);

This function is typically used to register the revision of a base class to use for the specified version of the type (see Type Revisions and Versions).

This function is used to register a singleton object cppObject, with a particular uri and typeName. Its version is a combination of versionMajor and versionMinor.

Installing a singleton type into a URI allows you to provide arbitrary functionality (methods and properties) to QML code without requiring individual instances of the type to be instantiated by the client.

Use this function to register an object of the given type T as a singleton type.

A QObject singleton type may be referenced via the type name with which it was registered; in turn this type name may be used as the target in a Connections type, or like any other type ID. However, there's one exception: a QObject singleton type property can't be aliased because the singleton type name does not identify an object within the same component as any other item.

NOTE: qmlRegisterSingleton can only be used when all types of that module are registered procedurally.

Usage:

// First, define your QObject which provides the functionality.
class SingletonTypeExample : public QObject
{
    Q_OBJECT
    Q_PROPERTY(int someProperty READ someProperty WRITE setSomeProperty NOTIFY somePropertyChanged)

public:
    explicit SingletonTypeExample(QObject* parent = nullptr) : QObject(parent) {}

    Q_INVOKABLE int doSomething()
    {
        setSomeProperty(5);
        return m_someProperty;
    }

    int someProperty() const { return m_someProperty; }
    void setSomeProperty(int val) {
        if (m_someProperty != val) {
            m_someProperty = val;
            emit somePropertyChanged(val);
        }
    }

signals:
    void somePropertyChanged(int newValue);

private:
    int m_someProperty = 0;
};

// Second, create an instance of the object

// allocate example before the engine to ensure that it outlives it
QScopedPointer<SingletonTypeExample> example(new SingletonTypeExample);
QQmlEngine engine;

// Third, register the singleton type provider with QML by calling this
// function in an initialization function.
qmlRegisterSingletonInstance("Qt.example.qobjectSingleton", 1, 0, "MyApi", example.get());

In order to use the registered singleton type in QML, you must import the URI with the corresponding version.

import QtQuick 2.0
import Qt.example.qobjectSingleton 1.0
Item {
    id: root
    property int someValue: MyApi.someProperty

    Component.onCompleted: {
        console.log(MyApi.doSomething())
    }
}

This function was introduced in Qt 5.14.

See Also▲

This function may be used to register a singleton type provider callback in a particular uri and typeName with a version specified in versionMajor and versionMinor.

Installing a singleton type allows developers to provide arbitrary functionality (methods and properties) to a client without requiring individual instances of the type to be instantiated by the client.

A singleton type may be either a QObject or a QJSValue. This function should be used to register a singleton type provider function which returns a QJSValue as a singleton type.

NOTE: QJSValue singleton type properties will not trigger binding re-evaluation if changed.

Usage:

// First, define the singleton type provider function (callback).
static QJSValue example_qjsvalue_singletontype_provider(QQmlEngine *engine, QJSEngine *scriptEngine)
{
    Q_UNUSED(engine)

    static int seedValue = 5;
    QJSValue example = scriptEngine->newObject();
    example.setProperty("someProperty", seedValue++);
    return example;
}

// Second, register the singleton type provider with QML by calling this function in an initialization function.
qmlRegisterSingletonType("Qt.example.qjsvalueApi", 1, 0, "MyApi", example_qjsvalue_singletontype_provider);

Alternatively, you can use a C++11 lambda:

qmlRegisterSingletonType("Qt.example.qjsvalueApi", 1, 0, "MyApi", [](QQmlEngine *engine, QJSEngine *scriptEngine) -> QJSValue {
    Q_UNUSED(engine)

    static int seedValue = 5;
    QJSValue example = scriptEngine->newObject();
    example.setProperty("someProperty", seedValue++);
    return example;
});

In order to use the registered singleton type in QML, you must import the singleton type.

import QtQuick 2.0
import Qt.example.qjsvalueApi 1.0 as ExampleApi
Item {
    id: root
    property int someValue: ExampleApi.MyApi.someProperty
}

See Also▲

This function may be used to register a singleton type provider callback in a particular uri and typeName with a version specified in versionMajor and versionMinor.

Installing a singleton type into a uri allows developers to provide arbitrary functionality (methods and properties) to clients without requiring individual instances ot the type to be instantiated by the client.

A singleton type may be either a QObject or a QJSValue. This function should be used to register a singleton type provider function which returns a QObject of the given type T as a singleton type.

A QObject singleton type may be referenced via the type name with which it was registered, and this typename may be used as the target in a Connections type or otherwise used as any other type id would. One exception to this is that a QObject singleton type property may not be aliased.

NOTE: A QObject singleton type instance returned from a singleton type provider is owned by the QML engine unless the object has explicit QQmlEngine::CppOwnership flag set.

Usage:

// First, define your QObject which provides the functionality.
class SingletonTypeExample : public QObject
{
    Q_OBJECT
    Q_PROPERTY (int someProperty READ someProperty WRITE setSomeProperty NOTIFY somePropertyChanged)

public:
    SingletonTypeExample(QObject *parent = nullptr)
        : QObject(parent), m_someProperty(0)
    {
    }

    ~SingletonTypeExample() {}

    Q_INVOKABLE int doSomething() { setSomeProperty(5); return m_someProperty; }

    int someProperty() const { return m_someProperty; }
    void setSomeProperty(int val) { m_someProperty = val; emit somePropertyChanged(val); }

signals:
    void somePropertyChanged(int newValue);

private:
    int m_someProperty;
};

// Second, define the singleton type provider function (callback).
static QObject *example_qobject_singletontype_provider(QQmlEngine *engine, QJSEngine *scriptEngine)
{
    Q_UNUSED(engine)
    Q_UNUSED(scriptEngine)

    SingletonTypeExample *example = new SingletonTypeExample();
    return example;
}

// Third, register the singleton type provider with QML by calling this function in an initialization function.
qmlRegisterSingletonType<SingletonTypeExample>("Qt.example.qobjectSingleton", 1, 0, "MyApi", example_qobject_singletontype_provider);

Alternatively, you can use a C++11 lambda:

qmlRegisterSingletonType<SingletonTypeExample>("Qt.example.qobjectSingleton", 1, 0, "MyApi", [](QQmlEngine *engine, QJSEngine *scriptEngine) -> QObject * {
    Q_UNUSED(engine)
    Q_UNUSED(scriptEngine)

    SingletonTypeExample *example = new SingletonTypeExample();
    return example;
});

In order to use the registered singleton type in QML, you must import the singleton type.

import QtQuick 2.0
import Qt.example.qobjectSingleton 1.0
Item {
    id: root
    property int someValue: MyApi.someProperty

    Component.onCompleted: {
        someValue = MyApi.doSomething()
    }
}

See Also▲

This function overloads qmlRegisterSingletonType.

This function was introduced in Qt 5.14.

This function may be used to register a singleton type with the name qmlName, in the library imported from uri having the version number composed from versionMajor and versionMinor. The type is defined by the QML file located at url. The url must be an absolute URL, i.e. url.isRelative() == false.

In addition the type's QML file must have pragma Singleton statement among its import statements.

A singleton type may be referenced via the type name with which it was registered, and this typename may be used as the target in a Connections type or otherwise used as any other type id would. One exception to this is that a singleton type property may not be aliased (because the singleton type name does not identify an object within the same component as any other item).

Usage:

// First, define your QML singleton type which provides the functionality.
pragma Singleton
import QtQuick 2.0
Item {
    property int testProp1: 125
}

// Second, register the QML singleton type by calling this function in an initialization function.
qmlRegisterSingletonType(QUrl("file:///absolute/path/SingletonType.qml"), "Qt.example.qobjectSingleton", 1, 0, "RegisteredSingleton");

In order to use the registered singleton type in QML, you must import the singleton type.

import QtQuick 2.0
import Qt.example.qobjectSingleton 1.0
Item {
    id: root
    property int someValue: RegisteredSingleton.testProp1
}

It is also possible to have QML singleton types registered without using the qmlRegisterSingletonType function. That can be done by adding a pragma Singleton statement among the imports of the type's QML file. In addition the type must be defined in a qmldir file with a singleton keyword and the qmldir must be imported by the QML files using the singleton.

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This template function registers the C++ type in the QML system with the name qmlName, in the library imported from uri having the version number composed from versionMajor and versionMinor.

Returns the QML type id.

There are two forms of this template function:

template<typename T>
int qmlRegisterType(const char *uri, int versionMajor, int versionMinor, const char *qmlName);

template<typename T, int metaObjectRevision>
int qmlRegisterType(const char *uri, int versionMajor, int versionMinor, const char *qmlName);

The former is the standard form which registers the type T as a new type. The latter allows a particular revision of a class to be registered in a specified version (see Type Revisions and Versions).

For example, this registers a C++ class MySliderItem as a QML type named Slider for version 1.0 of a type namespace called "com.mycompany.qmlcomponents":

qmlRegisterType<MySliderItem>("com.mycompany.qmlcomponents", 1, 0, "Slider");

Once this is registered, the type can be used in QML by importing the specified type namespace and version number:

import com.mycompany.qmlcomponents 1.0

Slider {
    // ...
}

Note that it's perfectly reasonable for a library to register types to older versions than the actual version of the library. Indeed, it is normal for the new library to allow QML written to previous versions to continue to work, even if more advanced versions of some of its types are available.

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This function registers a type in the QML system with the name qmlName, in the library imported from uri having the version number composed from versionMajor and versionMinor. The type is defined by the QML file located at url. The url must be an absolute URL, i.e. url.isRelative() == false.

Normally QML files can be loaded as types directly from other QML files, or using a qmldir file. This function allows registration of files to types from C++ code, such as when the type mapping needs to be procedurally determined at startup.

Returns -1 if the registration was not successful.

This function registers a type in the QML system with the name qmlName, in the type namespace imported from uri having the version number composed from versionMajor and versionMinor, but any attempt to instantiate the type will produce the given error message.

Normally, the types exported by a plugin should be fixed. However, if a C++ type is not available, you should at least "reserve" the QML type name, and give the user of the unavailable type a meaningful error message.

Returns the QML type id.

Example:

#ifdef NO_GAMES_ALLOWED
qmlRegisterTypeNotAvailable("MinehuntCore", 0, 1, "Game", "Get back to work, slacker!");
#else
qmlRegisterType<MinehuntGame>("MinehuntCore", 0, 1, "Game");
#endif

This will cause any QML which imports the "MinehuntCore" type namespace and attempts to use the type to produce an error message:

fun.qml: Get back to work, slacker!
   Game {
   ^

Without this, a generic "Game is not a type" message would be given.

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This function registers the staticMetaObject and its extension in the QML system with the name qmlName in the library imported from uri having version number composed from versionMajor and versionMinor.

An instance of the meta object cannot be created. An error message with the given reason is printed if the user attempts to create it.

This function is useful for registering Q_NAMESPACE namespaces.

Returns the QML type id.

For example:

namespace MyNamespace {
  Q_NAMESPACE
  enum MyEnum {
      Key1,
      Key2,
  };
  Q_ENUMS(MyEnum)
}

//...
qmlRegisterUncreatableMetaObject(MyNamespace::staticMetaObject, "io.qt", 1, 0, "MyNamespace", "Access to enums & flags only");

On the QML side, you can now use the registered enums:

Component.onCompleted: console.log(MyNamespace.Key2)

This function was introduced in Qt 5.8.

See Also▲

This template function registers the C++ type in the QML system with the name qmlName, in the library imported from uri having the version number composed from versionMajor and versionMinor.

While the type has a name and a type, it cannot be created, and the given error message will result if creation is attempted.

This is useful where the type is only intended for providing attached properties or enum values.

Returns the QML type id.

See Also▲

Returns the QML type id of a type that was registered with the name qmlName in a particular uri and a version specified in versionMajor and versionMinor.

This function returns the same value as the QML type registration functions such as qmlRegisterType() and qmlRegisterSingletonType().

If qmlName, uri and versionMajor match a registered type, but the specified minor version in versionMinor is higher, then the id of the type with the closest minor version is returned.

Returns -1 if no matching type was found or one of the given parameters was invalid.

This function was introduced in Qt 5.12.

See Also▲

Removes a module import previously registered with qmlRegisterModuleImport()

Calling this function makes sure that import of version importMajor.importMinor is not automatically imported anymore when uri of version moduleMajor is. The version resolution works the same way as with qmlRegisterModuleImport().

See Also▲

Prints warning messages that include the file and line number for the specified QML object.

When QML types produce logging messages, it improves traceability if they include the QML file and line number on which the particular instance was instantiated.

To include the file and line number, an object must be passed. If the file and line number is not available for that instance (either it was not instantiated by the QML engine or location information is disabled), "unknown location" will be used instead.

For example,