QQmlComponent#
The QQmlComponent
class encapsulates a QML component definition. More…
Synopsis#
Properties#
Functions#
def
create
(arg__1[, context=None[, forContext=None]])def
createObject
([parent=None[, properties={}]])def
createWithInitialProperties
(initialProperties[, context=None])def
creationContext
()def
engine
()def
errorString
()def
errors
()def
isBound
()def
isError
()def
isLoading
()def
isNull
()def
isReady
()def
progress
()def
setInitialProperties
(component, properties)def
status
()def
url
()
Virtual functions#
def
beginCreate
(arg__1)def
completeCreate
()def
create
([context=None])
Slots#
def
loadFromModule
(uri, typeName[, mode=QQmlComponent.CompilationMode.PreferSynchronous])def
loadUrl
(url)def
loadUrl
(url, mode)def
setData
(arg__1, baseUrl)
Signals#
def
progressChanged
(arg__1)def
statusChanged
(arg__1)
Note
This documentation may contain snippets that were automatically translated from C++ to Python. We always welcome contributions to the snippet translation. If you see an issue with the translation, you can also let us know by creating a ticket on https:/bugreports.qt.io/projects/PYSIDE
Detailed Description#
Components are reusable, encapsulated QML types with well-defined interfaces.
A QQmlComponent
instance can be created from a QML file. For example, if there is a main.qml
file like this:
The following code loads this QML file as a component, creates an instance of this component using create()
, and then queries the Item’s width value:
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
To create instances of a component in code where a QQmlEngine
instance is not available, you can use qmlContext()
or qmlEngine()
. For example, in the scenario below, child items are being created within a QQuickItem subclass:
void MyCppItem::init() { QQmlEngine *engine = qmlEngine(this); // Or: // QQmlEngine *engine = qmlContext(this)->engine(); QQmlComponent component(engine, QUrl::fromLocalFile("MyItem.qml")); QQuickItem *childItem = qobject_cast<QQuickItem*>(component.create()); childItem->setParentItem(this); }
Note that these functions will return null
when called inside the constructor of a QObject subclass, as the instance will not yet have a context nor engine.
Network Components#
If the URL passed to QQmlComponent
is a network resource, or if the QML document references a network resource, the QQmlComponent
has to fetch the network data before it is able to create objects. In this case, the QQmlComponent
will have a Loading
status
. An application will have to wait until the component is Ready
before calling create()
.
The following example shows how to load a QML file from a network resource. After creating the QQmlComponent
, it tests whether the component is loading. If it is, it connects to the statusChanged()
signal and otherwise calls the continueLoading()
method directly. Note that isLoading()
may be false for a network component if the component has been cached and is ready immediately.
MyApplication::MyApplication() { // ... component = new QQmlComponent(engine, QUrl("http://www.example.com/main.qml")); if (component->isLoading()) { QObject::connect(component, &QQmlComponent::statusChanged, this, &MyApplication::continueLoading); } else { continueLoading(); } } void MyApplication::continueLoading() { if (component->isError()) { qWarning() << component->errors(); } else { QObject *myObject = component->create(); } }
- class PySide6.QtQml.QQmlComponent([parent=None])#
PySide6.QtQml.QQmlComponent(arg__1[, parent=None])
PySide6.QtQml.QQmlComponent(arg__1, fileName[, parent=None])
PySide6.QtQml.QQmlComponent(arg__1, fileName, mode[, parent=None])
PySide6.QtQml.QQmlComponent(arg__1, url[, parent=None])
PySide6.QtQml.QQmlComponent(arg__1, url, mode[, parent=None])
PySide6.QtQml.QQmlComponent(engine, uri, typeName[, parent=None])
PySide6.QtQml.QQmlComponent(engine, uri, typeName, mode[, parent=None])
- Parameters:
mode –
CompilationMode
arg__1 –
PySide6.QtQml.QQmlEngine
fileName – str
engine –
PySide6.QtQml.QQmlEngine
url –
PySide6.QtCore.QUrl
typeName – str
uri – str
parent –
PySide6.QtCore.QObject
Create a QQmlComponent
with no data and give it the specified engine
and parent
. Set the data with setData()
.
Create a QQmlComponent
from the given fileName
and give it the specified parent
and engine
.
See also
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
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.
Relative paths will be resolved against baseUrl()
, which is the current working directory unless specified.
See also
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.
Relative paths will be resolved against baseUrl()
, which is the current working directory unless specified.
See also
Create a QQmlComponent
from the given uri
and typeName
and give it the specified parent
and engine
. If possible, the component will be loaded synchronously.
This is an overloaded function.
See also
Create a QQmlComponent
from the given uri
and typeName
and give it the specified parent
and engine
. If mode
is Asynchronous
, the component will be loaded and compiled asynchronously.
This is an overloaded function.
See also
Note
Properties can be used directly when from __feature__ import true_property
is used or via accessor functions otherwise.
- property PᅟySide6.QtQml.QQmlComponent.progress: float#
The progress of loading the component, from 0.0 (nothing loaded) to 1.0 (finished).
- Access functions:
progress
()Signal
progressChanged
(arg__1)
- property PᅟySide6.QtQml.QQmlComponent.status: Status#
The component’s current status
.
- Access functions:
status
()Signal
statusChanged
(arg__1)
- property PᅟySide6.QtQml.QQmlComponent.url: PySide6.QtCore.QUrl#
The component URL. This is the URL passed to either the constructor, or the loadUrl()
, or setData()
methods.
- Access functions:
url
()
- PySide6.QtQml.QQmlComponent.CompilationMode#
Specifies whether the QQmlComponent
should load the component immediately, or asynchonously.
Constant
Description
QQmlComponent.PreferSynchronous
Prefer loading/compiling the component immediately, blocking the thread. This is not always possible; for example, remote URLs will always load asynchronously.
QQmlComponent.Asynchronous
Load/compile the component in a background thread.
- PySide6.QtQml.QQmlComponent.Status#
Specifies the loading status of the QQmlComponent
.
Constant
Description
QQmlComponent.Null
This
QQmlComponent
has no data. CallloadUrl()
orsetData()
to add QML content.QQmlComponent.Ready
This
QQmlComponent
is ready andcreate()
may be called.QQmlComponent.Loading
This
QQmlComponent
is loading network data.QQmlComponent.Error
An error has occurred. Call
errors()
to retrieve a list oferrors
.
- PySide6.QtQml.QQmlComponent.beginCreate(arg__1)#
- Parameters:
arg__1 –
PySide6.QtQml.QQmlContext
- Return type:
Create an object instance from this component, within the specified context
. Returns None
if creation failed.
Note
This method provides advanced control over component instance creation. In general, programmers should use create()
to create object instances.
When QQmlComponent
constructs an instance, it occurs in three steps:
The object hierarchy is created, and constant values are assigned.
Property bindings are evaluated for the first time.
If applicable,
componentComplete()
is called on objects.
QQmlComponent::beginCreate() differs from create()
in that it only performs step 1. 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.
The ownership of the returned object instance is transferred to the caller.
Note
The categorization of bindings into constant values and actual bindings is intentionally unspecified and may change between versions of Qt and depending on whether and how you are using qmlcachegen . You should not rely on any particular binding to be evaluated either before or after beginCreate() returns. For example a constant expression like MyType.EnumValue may be recognized as such at compile time or deferred to be executed as binding. The same holds for constant expressions like -(5) or “a” + “ constant string”.
See also
completeCreate()
ObjectOwnership
- PySide6.QtQml.QQmlComponent.completeCreate()#
This method provides advanced control over component instance creation. In general, programmers should use create()
to create a component.
This function completes the component creation begun with beginCreate()
and must be called afterwards.
See also
- PySide6.QtQml.QQmlComponent.create([context=None])#
- Parameters:
context –
PySide6.QtQml.QQmlContext
- Return type:
Create an object instance from this component, within the specified context
. Returns None
if creation failed.
If context
is None
(the default), it will create the instance in the root context
of the engine.
The ownership of the returned object instance is transferred to the caller.
If the object being created from this component is a visual item, it must have a visual parent, which can be set by calling QQuickItem::setParentItem(). See Concepts - Visual Parent in Qt Quick for more details.
See also
ObjectOwnership
- PySide6.QtQml.QQmlComponent.create(arg__1[, context=None[, forContext=None]])
- Parameters:
arg__1 –
PySide6.QtQml.QQmlIncubator
context –
PySide6.QtQml.QQmlContext
forContext –
PySide6.QtQml.QQmlContext
Create an object instance from this component using the provided incubator
. context
specifies the context within which to create the object instance.
If context
is None
(by default), it will create the instance in the engine’s root context
.
forContext
specifies a context that this object creation depends upon. If the forContext
is being created asynchronously, and the IncubationMode
is AsynchronousIfNested
, this object will also be created asynchronously. If forContext
is None
(by default), the context
will be used for this decision.
The created object and its creation status are available via the incubator
.
See also
- PySide6.QtQml.QQmlComponent.createObject([parent=None[, properties={}]])#
- Parameters:
parent –
PySide6.QtCore.QObject
properties – Dictionary with keys of type .QString and values of type QVariant.
- Return type:
- PySide6.QtQml.QQmlComponent.createWithInitialProperties(initialProperties[, context=None])#
- Parameters:
initialProperties – Dictionary with keys of type .QString and values of type QVariant.
context –
PySide6.QtQml.QQmlContext
- Return type:
Create an object instance of this component, within the specified context
, and initialize its top-level properties with initialProperties
.
If any of the initialProperties
cannot be set, a warning is issued. If there are unset required properties, the object creation fails and returns nullptr
, in which case isError()
will return true
.
See also
- PySide6.QtQml.QQmlComponent.creationContext()#
- Return type:
Returns the QQmlContext
the component was created in. This is only valid for components created directly from QML.
- PySide6.QtQml.QQmlComponent.engine()#
- Return type:
Returns the QQmlEngine
of this component.
- PySide6.QtQml.QQmlComponent.errorString()#
- Return type:
str
Returns the list of errors that occurred during the last compile or create operation. An empty list is returned if isError()
is not set.
- PySide6.QtQml.QQmlComponent.isBound()#
- Return type:
bool
Returns true if the component was created in a QML files that specifies pragma ComponentBehavior: Bound
, otherwise returns false.
- PySide6.QtQml.QQmlComponent.isError()#
- Return type:
bool
Returns true if status()
== Error
.
- PySide6.QtQml.QQmlComponent.isLoading()#
- Return type:
bool
Returns true if status()
== Loading
.
- PySide6.QtQml.QQmlComponent.isNull()#
- Return type:
bool
Returns true if status()
== Null
.
- PySide6.QtQml.QQmlComponent.isReady()#
- Return type:
bool
Returns true if status()
== Ready
.
- PySide6.QtQml.QQmlComponent.loadFromModule(uri, typeName[, mode=QQmlComponent.CompilationMode.PreferSynchronous])#
- Parameters:
uri – str
typeName – str
mode –
CompilationMode
Load the QQmlComponent
for typeName
in the module uri
. If the type is implemented via a QML file, mode
is used to load it. Types backed by C++ are always loaded synchronously.
QQmlEngine engine; QQmlComponent component(&engine); component.loadFromModule("QtQuick", "Item"); // once the component is ready std::unique_ptr<QObject> item(component.create()); Q_ASSERT(item->metaObject() == &QQuickItem::staticMetaObject);See also
- PySide6.QtQml.QQmlComponent.loadUrl(url)#
- Parameters:
url –
PySide6.QtCore.QUrl
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.
Relative paths will be resolved against baseUrl()
, which is the current working directory unless specified.
- PySide6.QtQml.QQmlComponent.loadUrl(url, mode)
- Parameters:
url –
PySide6.QtCore.QUrl
mode –
CompilationMode
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.
Relative paths will be resolved against baseUrl()
, which is the current working directory unless specified.
- PySide6.QtQml.QQmlComponent.progress()#
- Return type:
float
Getter of property progress
.
- PySide6.QtQml.QQmlComponent.progressChanged(arg__1)#
- Parameters:
arg__1 – float
Emitted whenever the component’s loading progress changes. progress
will be the current progress between 0.0 (nothing loaded) and 1.0 (finished).
Notification signal of property progress
.
- PySide6.QtQml.QQmlComponent.setData(arg__1, baseUrl)#
- Parameters:
arg__1 –
PySide6.QtCore.QByteArray
baseUrl –
PySide6.QtCore.QUrl
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.
- PySide6.QtQml.QQmlComponent.setInitialProperties(component, properties)#
- Parameters:
component –
PySide6.QtCore.QObject
properties – Dictionary with keys of type .QString and values of type QVariant.
Set top-level properties
of the component
.
This method provides advanced control over component instance creation. In general, programmers should use createWithInitialProperties
to create a component.
Use this method after beginCreate
and before completeCreate
has been called. If a provided property does not exist, a warning is issued.
Getter of property status
.
Emitted whenever the component’s status changes. status
will be the new status.
Notification signal of property status
.
- PySide6.QtQml.QQmlComponent.url()#
- Return type:
Getter of property url
.