Component QML Type

The progress of loading the component, from 0.0 (nothing loaded) to 1.0 (finished).

This property holds the status of component loading. The status can be one of the following:

The component URL. This is the URL that was used to construct the component.

Emitted after the object has been instantiated. This can be used to execute script code at startup, once the full QML environment has been established.

The onCompleted signal handler can be declared on any object. The order of running the handlers is undefined.

Rectangle {
    Component.onCompleted: console.log("Completed Running!")
    Rectangle {
        Component.onCompleted: console.log("Nested Completed Running!")
    }
}

Emitted as the object begins destruction. This can be used to undo work done in response to the completed() signal, or other imperative code in your application.

The onDestruction signal handler can be declared on any object. The order of running the handlers is undefined.

Rectangle {
    Component.onDestruction: console.log("Destruction Beginning!")
    Rectangle {
        Component.onDestruction: console.log("Nested Destruction Beginning!")
    }
}

See also Qt Qml.

Creates and returns an object instance of this component that will have the given parent and properties. The properties argument is optional. Returns null if object creation fails.

The object will be created in the same context as the one in which the component was created. This function will always return null when called on components which were not created in QML.

If you wish to create an object without setting a parent, specify null for the parent value. Note that if the returned object is to be displayed, you must provide a valid parent value or set the returned object's parent property, otherwise the object will not be visible.

If a parent is not provided to createObject(), a reference to the returned object must be held so that it is not destroyed by the garbage collector. This is true regardless of whether Item::parent is set afterwards, because setting the Item parent does not change object ownership. Only the graphical parent is changed.

As of QtQuick 1.1, this method accepts an optional properties argument that specifies a map of initial property values for the created object. These values are applied before the object creation is finalized. This is more efficient than setting property values after object creation, particularly where large sets of property values are defined, and also allows property bindings to be set up (using Qt.binding) before the object is created.

The properties argument is specified as a map of property-value items. For example, the code below creates an object with initial x and y values of 100 and 100, respectively:

const component = Qt.createComponent("Button.qml");
if (component.status === Component.Ready) {
    component.createObject(parent, { x: 100, y: 100 });
}

Dynamically created instances can be deleted with the destroy() method. See Dynamic QML Object Creation from JavaScript for more information.

See also incubateObject().

Returns a human-readable description of any error.

The string includes the file, location, and description of each error. If multiple errors are present, they are separated by a newline character.

If no errors are present, an empty string is returned.

Creates an incubator for an instance of this component. Incubators allow new component instances to be instantiated asynchronously and do not cause freezes in the UI.

The parent argument specifies the parent the created instance will have. Omitting the parameter or passing null will create an object with no parent. In this case, a reference to the created object must be held so that it is not destroyed by the garbage collector.

The properties argument is specified as a map of property-value items which will be set on the created object during its construction. mode may be Qt.Synchronous or Qt.Asynchronous, and controls whether the instance is created synchronously or asynchronously. The default is asynchronous. In some circumstances, even if Qt.Synchronous is specified, the incubator may create the object asynchronously. This happens if the component calling incubateObject() is itself being created asynchronously.

All three arguments are optional.

If successful, the method returns an incubator, otherwise null. The incubator has the following properties:

• status - The status of the incubator. Valid values are Component.Ready, Component.Loading and Component.Error.
• object - The created object instance. Will only be available once the incubator is in the Ready status.
• onStatusChanged - Specifies a callback function to be invoked when the status changes. The status is passed as a parameter to the callback.
• forceCompletion() - Call to complete incubation synchronously.

The following example demonstrates how to use an incubator:

const component = Qt.createComponent("Button.qml");

const incubator = component.incubateObject(parent, { x: 10, y: 10 });
if (incubator.status !== Component.Ready) {
    incubator.onStatusChanged = function(status) {
        if (status === Component.Ready) {
            print("Object", incubator.object, "is now ready!");
        }
    };
} else {
    print("Object", incubator.object, "is ready immediately!");
}

Dynamically created instances can be deleted with the destroy() method. See Dynamic QML Object Creation from JavaScript for more information.

See also createObject().