PySide6.QtQml.QQmlListReference

class QQmlListReference

The QQmlListReference class allows the manipulation of QQmlListProperty properties.

Details

QQmlListReference allows C++ programs to read from, and assign values to a QML list property in a simple and type-safe way. The main advantage over using QQmlListProperty itself is its type erasure: QQmlListReference is not a template, but can be used for QQmlListProperties of any type. Furthermore it watches the owner object for deletion and does not allow the QQmlListProperty to be accessed anymore if its owner has been deleted.

You can create a QQmlListReference from either an object and a property name or from a QVariant. These two are equivalent:

QQmlListReference ref1(object, "children");

const QVariant var = object->property("children");
QQmlListReference ref2(var);

Not all QQmlListReferences support all operations. Methods like canAppend() , canAt() , canClear() , and canCount() allow programs to query whether an operation is supported on a given property. The availability of the methods depends on the methods implemented by the underlying QQmlListProperty . When constructing a QQmlListProperty by manually passing the accessor functions you can restrict access to the list by passing nullptr to some of them. QQmlListReference will recognize those and report them as unavailable.

QQmlListReference s are type-safe. Only QObjects that derive of the correct base class can be added to the list. The listElementType() method can be used to query the QMetaObject of the QObject type that can be added. Attempting to add objects of an incorrect type to a list property will fail.

Like with other lists, when accessing a list element by index, it is the callers responsibility to ensure that it does not request an out of range element. Use the count() method before calling at() to this effect.

Synopsis

Methods

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

__init__()

Constructs an invalid instance.

__init__(variant)
Parameters:

variant – QQmlListReference

Constructs a QQmlListReference from a QVariant variant containing a QQmlListProperty . If variant does not contain a list property, an invalid QQmlListReference is created. If the object owning the list property is destroyed after the reference is constructed, it will automatically become invalid. That is, it is safe to hold QQmlListReference instances even after the object is deleted.

__init__(variant)
Parameters:

variant – object

Constructs a QQmlListReference from a QVariant variant containing a QQmlListProperty . If variant does not contain a list property, an invalid QQmlListReference is created. If the object owning the list property is destroyed after the reference is constructed, it will automatically become invalid. That is, it is safe to hold QQmlListReference instances even after the object is deleted.

__init__(o, property)
Parameters:

Constructs a QQmlListReference for object's property. If property is not a list property, an invalid QQmlListReference is created. If object is destroyed after the reference is constructed, it will automatically become invalid. That is, it is safe to hold QQmlListReference instances even after object is deleted.

__init__(variant, engine)
Parameters:

Note

This function is deprecated.

Use the constructors without QQmlEngine argument instead.

Constructs a QQmlListReference from a QVariant variant containing a QQmlListProperty . If variant does not contain a list property, an invalid QQmlListReference is created. If the object owning the list property is destroyed after the reference is constructed, it will automatically become invalid. That is, it is safe to hold QQmlListReference instances even after the object is deleted.

The engine is unused.

__init__(o, property, engine)
Parameters:

Note

This function is deprecated.

Use the constructors without QQmlEngine argument instead.

Constructs a QQmlListReference for object's property. If property is not a list property, an invalid QQmlListReference is created. If object is destroyed after the reference is constructed, it will automatically become invalid. That is, it is safe to hold QQmlListReference instances even after object is deleted.

The engine is unused.

append(object)
Parameters:

object – QObject

Return type:

bool

Appends object to the list. Returns true if the operation succeeded, otherwise false.

See also

canAppend()

at(index)
Parameters:

index – int

Return type:

QObject

Returns the list element at index, or None if the operation failed.

See also

canAt()

canAppend()
Return type:

bool

Returns true if the list property can be appended to, otherwise false. Returns false if the reference is invalid.

See also

append()

canAt()
Return type:

bool

Returns true if the list property can queried by index, otherwise false. Returns false if the reference is invalid.

See also

at()

canClear()
Return type:

bool

Returns true if the list property can be cleared, otherwise false. Returns false if the reference is invalid.

See also

clear()

canCount()
Return type:

bool

Returns true if the list property can be queried for its element count, otherwise false. Returns false if the reference is invalid.

See also

count()

canRemoveLast()
Return type:

bool

Returns true if the last item can be removed from the list property, otherwise false. Returns false if the reference is invalid.

See also

removeLast()

canReplace()
Return type:

bool

Returns true if items in the list property can be replaced, otherwise false. Returns false if the reference is invalid.

See also

replace()

clear()
Return type:

bool

Clears the list. Returns true if the operation succeeded, otherwise false.

See also

canClear()

count()
Return type:

int

Returns the number of items in the list, or 0 if the operation failed.

isManipulable()
Return type:

bool

Return true if at() , count() , append() , and either clear() or removeLast() are implemented, so you can manipulate the list.

Mind that replace() and removeLast() can be emulated by stashing all items and rebuilding the list using clear() and append() . Therefore, they are not required for the list to be manipulable. Furthermore, clear() can be emulated using removeLast() .

isReadable()
Return type:

bool

Return true if at() and count() are implemented, so you can access the elements.

isValid()
Return type:

bool

Returns true if the instance refers to a valid list property, otherwise false.

listElementType()
Return type:

QMetaObject

Returns the QMetaObject for the elements stored in the list property, or None if the reference is invalid.

The QMetaObject can be used ahead of time to determine whether a given instance can be added to a list. If you didn’t pass an engine on construction this may return nullptr.

object()
Return type:

QObject

Returns the list property’s object. Returns None if the reference is invalid.

__eq__(other)
Parameters:

other – QQmlListReference

Return type:

bool

Compares this QQmlListReference to other, and returns true if they are equal. The two are only considered equal if one was created from the other via copy assignment or copy construction.

Note

Independently created references to the same object are not considered to be equal.

removeLast()
Return type:

bool

Removes the last item in the list. Returns true if the operation succeeded, otherwise false.

See also

canRemoveLast()

replace(index, object)
Parameters:
Return type:

bool

Replaces the item at index in the list with object. Returns true if the operation succeeded, otherwise false.

See also

canReplace()

size()
Return type:

int

Returns the number of items in the list, or 0 if the operation failed.