The QQmlListReference class allows the manipulation of \l QQmlListProperty properties. More...

#include <qqmllist.h>

Collaboration diagram for QQmlListReference:

Public Member Functions
	QQmlListReference ()
	Constructs an invalid instance.

	QQmlListReference (const QVariant &variant)

	QQmlListReference (QObject o, const char property)
	Constructs a QQmlListReference for object's property.

	QQmlListReference (const QQmlListReference &)

QQmlListReference &	operator= (const QQmlListReference &)

	~QQmlListReference ()

bool	isValid () const
	Returns true if the instance refers to a valid list property, otherwise false.

QObject *	object () const
	Returns the list property's object.

const QMetaObject *	listElementType () const
	Returns the QMetaObject for the elements stored in the list property, or \nullptr if the reference is invalid.

bool	canAppend () const
	Returns true if the list property can be appended to, otherwise false.

bool	canAt () const
	Returns true if the list property can queried by index, otherwise false.

bool	canClear () const
	Returns true if the list property can be cleared, otherwise false.

bool	canCount () const
	Returns true if the list property can be queried for its element count, otherwise false.

bool	canReplace () const
	Returns true if items in the list property can be replaced, otherwise false.

bool	canRemoveLast () const
	Returns true if the last item can be removed from the list property, otherwise false.

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

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

bool	append (QObject *) const
	Appends object to the list.

QObject *	at (qsizetype) const
	Returns the list element at index, or \nullptr if the operation failed.

bool	clear () const
	Clears the list.

qsizetype	count () const
	Returns the number of items in the list, or 0 if the operation failed.

qsizetype	size () const

bool	replace (qsizetype, QObject *) const
	Replaces the item at index in the list with object.

bool	removeLast () const
	Removes the last item in the list.

bool	operator== (const QQmlListReference &other) const
	Compares this QQmlListReference to other, and returns `true` if they are equal.

Friends
class	QQmlListReferencePrivate

Detailed Description

The QQmlListReference class allows the manipulation of \l QQmlListProperty properties.

Since: 5.0 \inmodule QtQml

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 \l 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 \l 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 \l QQmlListProperty. When constructing a \l 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.

\l{QQmlListReference}s are type-safe. Only \l{QObject}s that derive of the correct base class can be added to the list. The listElementType() method can be used to query the \l QMetaObject of the \l 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.

Definition at line 182 of file qqmllist.h.

Constructor & Destructor Documentation

◆ QQmlListReference() [1/4]

QQmlListReference::QQmlListReference ( )

Constructs an invalid instance.

Definition at line 108 of file qqmllist.cpp.

◆ QQmlListReference() [2/4]

QQmlListReference::QQmlListReference ( const QVariant & variant )

explicit

Since: 6.1

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.

Definition at line 155 of file qqmllist.cpp.

◆ QQmlListReference() [3/4]

QQmlListReference::QQmlListReference	(	QObject *	object,
		const char *	property )

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.

Definition at line 177 of file qqmllist.cpp.

◆ QQmlListReference() [4/4]

QQmlListReference::QQmlListReference ( const QQmlListReference & o )

Definition at line 197 of file qqmllist.cpp.

◆ ~QQmlListReference()

QQmlListReference::~QQmlListReference ( )

Definition at line 213 of file qqmllist.cpp.

Member Function Documentation

◆ append()

bool QQmlListReference::append ( QObject * object ) const

Appends object to the list.

Returns true if the operation succeeded, otherwise false.

See also: canAppend()

Definition at line 349 of file qqmllist.cpp.

◆ at()

QObject * QQmlListReference::at ( qsizetype index ) const

Returns the list element at index, or \nullptr if the operation failed.

See also: canAt()

Definition at line 366 of file qqmllist.cpp.