The QQmlListReference class allows the manipulation of QQmlListProperty 特性。 更多...
| 头： | #include <QQmlListReference> |
| CMake: |
find_package(Qt6 COMPONENTS Qml REQUIRED)
target_link_libraries(mytarget PRIVATE Qt6::Qml) |
| qmake: | QT += qml |
| Since: | Qt 5.0 |
| QQmlListReference (QObject * object , const char * property , QQmlEngine * engine = nullptr) | |
| QQmlListReference (const QVariant & variant , QQmlEngine * engine = nullptr) | |
| QQmlListReference () | |
| bool | append (QObject * object ) const |
| QObject * | at (qsizetype index ) const |
| bool | canAppend () const |
| bool | canAt () const |
| bool | canClear () const |
| bool | canCount () const |
| bool | canRemoveLast () const |
| bool | canReplace () const |
| bool | clear () const |
| qsizetype | count () const |
| bool | isManipulable () const |
| bool | isReadable () const |
| bool | isValid () const |
| const QMetaObject * | listElementType () const |
| QObject * | object () const |
| bool | removeLast () const |
| bool | replace (qsizetype index , QObject * object ) const |
| qsizetype | size () const |
| bool | operator== (const QQmlListReference & other ) const |
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 () 和 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 的 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 ().
Constructs a QQmlListReference for object 's property 。若 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 被删除。
engine is required to look up the element type, which may be a dynamically created QML type. If it's omitted, only pre-registered types are available. The element type is needed when inserting values into the list and when the value meta type is explicitly retrieved.
[since 6.1]
QQmlListReference::
QQmlListReference
(const
QVariant
&
variant
,
QQmlEngine
*
engine
= nullptr)
Constructs a QQmlListReference from a QVariant variant 包含 QQmlListProperty 。若 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.
engine is required to look up the element type, which may be a dynamically created QML type. If it's omitted, only pre-registered types are available. The element type is needed when inserting values into the list and when the value meta type is explicitly retrieved.
该函数在 Qt 6.1 引入。
Constructs an invalid instance.
追加 object to the list. Returns true if the operation succeeded, otherwise false.
另请参阅 canAppend ().
Returns the list element at index , or 0 if the operation failed.
另请参阅 canAt ().
Returns true if the list property can be appended to, otherwise false. Returns false if the reference is invalid.
另请参阅 append ().
Returns true if the list property can queried by index, otherwise false. Returns false if the reference is invalid.
另请参阅 at ().
Returns true if the list property can be cleared, otherwise false. Returns false if the reference is invalid.
另请参阅 clear ().
Returns true if the list property can be queried for its element count, otherwise false. Returns false if the reference is invalid.
另请参阅 count ().
Returns true if the last item can be removed from the list property, otherwise false. Returns false if the reference is invalid.
另请参阅 removeLast ().
Returns true if items in the list property can be replaced, otherwise false. Returns false if the reference is invalid.
另请参阅 replace ().
Clears the list. Returns true if the operation succeeded, otherwise false.
另请参阅 canClear ().
Returns the number of objects in the list, or 0 if the operation failed.
返回 True 若 at (), count (), append (), and either clear () 或 removeLast () are implemented, so you can manipulate the list.
Mind that replace () 和 removeLast () can be emulated by stashing all items and rebuilding the list using clear () 和 append (). Therefore, they are not required for the list to be manipulable. Furthermore, clear () can be emulated using removeLast ().
另请参阅 isReadable (), at (), count (), append (), clear (), replace ()，和 removeLast ().
返回 True 若 at () 和 count () are implemented, so you can access the elements.
另请参阅 isManipulable (), at ()，和 count ().
Returns true if the instance refers to a valid list property, otherwise false.
返回
QMetaObject
for the elements stored in the list property, or
nullptr
if the reference is invalid.
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.
Returns the list property's object. Returns
nullptr
if the reference is invalid.
Removes the last item in the list. Returns true if the operation succeeded, otherwise false.
另请参阅 canRemoveLast ().
Replaces the item at index in the list with object . Returns true if the operation succeeded, otherwise false.
另请参阅 canReplace ().
[since 6.2]
qsizetype
QQmlListReference::
size
() const
Returns the number of objects in the list, or 0 if the operation failed.
该函数在 Qt 6.2 引入。
Compares this
QQmlListReference
to
other
，并返回
true
if they are equal. The two are only considered equal if one was created from the other via copy assignment or copy construction.
注意： Independently created references to the same object are not considered to be equal.