QQmlComponent Class

 import QtQuick 2.0

 Item {
     width: 200
     height: 200
 }

 QQmlEngine *engine = new QQmlEngine;
 QQmlComponent component(engine, QUrl::fromLocalFile("main.qml"));

 QObject *myObject = component.create();
 QQuickItem *item = qobject_cast<QQuickItem*>(myObject);
 int width = item->width();  // width = 200

 MyApplication::MyApplication()
 {
     // ...
     component = new QQmlComponent(engine, QUrl("http://www.example.com/main.qml"));
     if (component->isLoading())
         QObject::connect(component, SIGNAL(statusChanged(QQmlComponent::Status)),
                          this, SLOT(continueLoading()));
     else
         continueLoading();
 }

 void MyApplication::continueLoading()
 {
     if (component->isError()) {
         qWarning() << component->errors();
     } else {
         QObject *myObject = component->create();
     }
 }

Member Function Documentation

QQmlComponent::QQmlComponent(QQmlEngine * engine, QObject * parent = 0)

Create a QQmlComponent with no data and give it the specified engine and parent. Set the data with setData().

QQmlComponent::QQmlComponent(QQmlEngine * engine, const QString & fileName, QObject * parent = 0)

Create a QQmlComponent from the given fileName and give it the specified parent and engine.

See also loadUrl().

QQmlComponent::QQmlComponent(QQmlEngine * engine, const QString & fileName, CompilationMode mode, QObject * parent = 0)

Create a QQmlComponent from the given fileName and give it the specified parent and engine. If mode is Asynchronous, the component will be loaded and compiled asynchronously.

See also loadUrl().

QQmlComponent::QQmlComponent(QQmlEngine * engine, const QUrl & url, QObject * parent = 0)

Create a QQmlComponent from the given url and give it the specified parent and engine.

Ensure that the URL provided is full and correct, in particular, use QUrl::fromLocalFile() when loading a file from the local filesystem.

See also loadUrl().

QQmlComponent::QQmlComponent(QQmlEngine * engine, const QUrl & url, CompilationMode mode, QObject * parent = 0)

Create a QQmlComponent from the given url and give it the specified parent and engine. If mode is Asynchronous, the component will be loaded and compiled asynchronously.

Ensure that the URL provided is full and correct, in particular, use QUrl::fromLocalFile() when loading a file from the local filesystem.

See also loadUrl().

QQmlComponent::~QQmlComponent() [virtual]

Destruct the QQmlComponent.

QObject * QQmlComponent::beginCreate(QQmlContext * publicContext) [virtual]

This method provides more advanced control over component instance creation. In general, programmers should use QQmlComponent::create() to create a component.

Create an object instance from this component. Returns 0 if creation failed. publicContext specifies the context within which to create the object instance.

When QQmlComponent constructs an instance, it occurs in three steps:

1. The object hierarchy is created, and constant values are assigned.
2. Property bindings are evaluated for the the first time.
3. If applicable, QQmlParserStatus::componentComplete() is called on objects.

QQmlComponent::beginCreate() differs from QQmlComponent::create() in that it only performs step 1. QQmlComponent::completeCreate() must be called to complete steps 2 and 3.

This breaking point is sometimes useful when using attached properties to communicate information to an instantiated component, as it allows their initial values to be configured before property bindings take effect.

void QQmlComponent::completeCreate() [virtual]

This method provides more advanced control over component instance creation. In general, programmers should use QQmlComponent::create() to create a component.

Complete a component creation begin with QQmlComponent::beginCreate().

QObject * QQmlComponent::create(QQmlContext * context = 0) [virtual]

Create an object instance from this component. Returns 0 if creation failed. context specifies the context within which to create the object instance.

If context is 0 (the default), it will create the instance in the engine' s root context.

void QQmlComponent::create(QQmlIncubator &, QQmlContext * context = 0, QQmlContext * forContext = 0)

void QQmlComponent::createObject(QQmlV8Function *) [protected]

QQmlContext * QQmlComponent::creationContext() const

Returns the QQmlContext the component was created in. This is only valid for components created directly from QML.

QList<QQmlError> QQmlComponent::errors() const

Return the list of errors that occurred during the last compile or create operation. An empty list is returned if isError() is not set.

void QQmlComponent::incubateObject(QQmlV8Function *) [protected]

bool QQmlComponent::isError() const

Returns true if status() == QQmlComponent::Error.

bool QQmlComponent::isLoading() const

Returns true if status() == QQmlComponent::Loading.

bool QQmlComponent::isNull() const

Returns true if status() == QQmlComponent::Null.

bool QQmlComponent::isReady() const

Returns true if status() == QQmlComponent::Ready.

void QQmlComponent::loadUrl(const QUrl & url) [slot]

Load the QQmlComponent from the provided url.

Ensure that the URL provided is full and correct, in particular, use QUrl::fromLocalFile() when loading a file from the local filesystem.

void QQmlComponent::loadUrl(const QUrl & url, CompilationMode mode) [slot]

Load the QQmlComponent from the provided url. If mode is Asynchronous, the component will be loaded and compiled asynchronously.

Ensure that the URL provided is full and correct, in particular, use QUrl::fromLocalFile() when loading a file from the local filesystem.

void QQmlComponent::setData(const QByteArray & data, const QUrl & url) [slot]

Sets the QQmlComponent to use the given QML data. If url is provided, it is used to set the component name and to provide a base path for items resolved by this component.