QQmlListReference Class▲
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Header: QQmlListReference
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Since: Qt 5.0
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CMake:
find_package(Qt6 REQUIRED COMPONENTS Qml)
target_link_libraries(mytarget PRIVATE Qt6::Qml)
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qmake: QT += qml
Detailed Description▲
QQmlListReference allows C++ programs to read from, and assign values to a QML list property in a simple and type-safe way. A QQmlListReference can be created by passing an object and property name or through a QQmlProperty instance. These two are equivalent:
QQmlListReference ref1(object, "children");
QQmlProperty ref2(object, "children");
QQmlListReference ref2 = qvariant_cast<QQmlListReference>(ref2.read());Not all QML list properties support all operations. A set of methods, canAppend(), canAt(), canClear() and canCount() allow programs to query whether an operation is supported on a given property.
QML list properties are type-safe. Only QObject's that derive from the correct base class can be assigned to the list. The listElementType() method can be used to query the QMetaObject of the QObject type supported. Attempting to add objects of the incorrect type to a list property will fail.
Like with normal 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 using the count() method before calling at().
Member Function Documentation▲
QQmlListReference::QQmlListReference()▲
Constructs an invalid instance.
[explicit, since 6.1] QQmlListReference::QQmlListReference(const QVariant &variant)▲
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.
This function was introduced in Qt 6.1.
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.
bool QQmlListReference::append(QObject *object) const▲
Appends object to the list. Returns true if the operation succeeded, otherwise false.
See Also▲
See also canAppend()
QObject *QQmlListReference::at(qsizetype index) const▲
bool QQmlListReference::canAppend() const▲
Returns true if the list property can be appended to, otherwise false. Returns false if the reference is invalid.
See Also▲
See also append()
bool QQmlListReference::canAt() const▲
Returns true if the list property can queried by index, otherwise false. Returns false if the reference is invalid.
See Also▲
See also at()
bool QQmlListReference::canClear() const▲
Returns true if the list property can be cleared, otherwise false. Returns false if the reference is invalid.
See Also▲
See also clear()
bool QQmlListReference::canCount() const▲
Returns true if the list property can be queried for its element count, otherwise false. Returns false if the reference is invalid.
See Also▲
See also count()
bool QQmlListReference::canRemoveLast() const▲
Returns true if the last item can be removed from the list property, otherwise false. Returns false if the reference is invalid.
See Also▲
See also removeLast()
bool QQmlListReference::canReplace() const▲
Returns true if items in the list property can be replaced, otherwise false. Returns false if the reference is invalid.
See Also▲
See also replace()
bool QQmlListReference::clear() const▲
Clears the list. Returns true if the operation succeeded, otherwise false.
See Also▲
See also canClear()
qsizetype QQmlListReference::count() const▲
Returns the number of objects in the list, or 0 if the operation failed.
bool QQmlListReference::isManipulable() const▲
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().
See Also▲
See also isReadable(), at(), count(), append(), clear(), replace(), removeLast()
bool QQmlListReference::isReadable() const▲
Return true if at() and count() are implemented, so you can access the elements.
See Also▲
See also isManipulable(), at(), count()
bool QQmlListReference::isValid() const▲
Returns true if the instance refers to a valid list property, otherwise false.
const QMetaObject *QQmlListReference::listElementType() const▲
Returns the QMetaObject for the elements stored in the list property, or nullptr 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.
QObject *QQmlListReference::object() const▲
Returns the list property's object. Returns nullptr if the reference is invalid.
bool QQmlListReference::removeLast() const▲
Removes the last item in the list. Returns true if the operation succeeded, otherwise false.
See Also▲
See also canRemoveLast()
bool QQmlListReference::replace(qsizetype index, QObject *object) const▲
Replaces the item at index in the list with object. Returns true if the operation succeeded, otherwise false.
See Also▲
See also canReplace()
[since 6.2] qsizetype QQmlListReference::size() const▲
Returns the number of objects in the list, or 0 if the operation failed.
This function was introduced in Qt 6.2.
bool QQmlListReference::operator==(const QQmlListReference &other) const▲
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.
Independently created references to the same object are not considered to be equal.
Obsolete Members for QQmlListReference▲
The following members of class QQmlListReference are deprecated. We strongly advise against using them in new code.
Obsolete Member Function Documentation▲
[since 6.1] QQmlListReference::QQmlListReference(const QVariant &variant, QQmlEngine *engine)▲
This function is deprecated. We strongly advise against using it in new code.
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.
This function was introduced in Qt 6.1.
QQmlListReference::QQmlListReference(QObject *object, const char *property, QQmlEngine *engine)▲
This function is deprecated. We strongly advise against using it in new code.
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.