QExplicitlySharedDataPointer Class

Member Function Documentation

[noexcept] QExplicitlySharedDataPointer::QExplicitlySharedDataPointer()

Constructs a QExplicitlySharedDataPointer initialized with nullptr as d pointer.

[explicit noexcept] QExplicitlySharedDataPointer::QExplicitlySharedDataPointer(T *data)

Constructs a QExplicitlySharedDataPointer with d pointer set to data and increments data's reference count.

[noexcept] template <typename X> QExplicitlySharedDataPointer::QExplicitlySharedDataPointer(const QExplicitlySharedDataPointer<X> &o)

This copy constructor is different in that it allows o to be a different type of explicitly shared data pointer but one that has a compatible shared data object.

By default, the d pointer of o (of type X *) gets implicitly converted to the type T *; the result of this conversion is set as the d pointer of this, and the reference count of the shared data object is incremented.

However, if the macro QT_ENABLE_QEXPLICITLYSHAREDDATAPOINTER_STATICCAST is defined before including the QExplicitlySharedDataPointer header, then the d pointer of o undergoes a static_cast to the type T *. The result of the cast is then set as the d pointer of this, and the reference count of the shared data object is incremented.

    QExplicitlySharedDataPointer<Base> base(new Base);
    QExplicitlySharedDataPointer<Derived> derived(base); // !!! DANGER !!!

Starting from Qt 5.4 the cast is disabled by default. It is possible to enable it back by defining the QT_ENABLE_QEXPLICITLYSHAREDDATAPOINTER_STATICCAST macro, and therefore to allow old code (that relied on this feature) to compile without modifications.

[noexcept] QExplicitlySharedDataPointer::QExplicitlySharedDataPointer(const QExplicitlySharedDataPointer<T> &o)

This standard copy constructor sets the d pointer of this to the d pointer in o and increments the reference count of the shared data object.

[noexcept] QExplicitlySharedDataPointer::QExplicitlySharedDataPointer(QExplicitlySharedDataPointer<T> &&o)

Move-constructs a QExplicitlySharedDataPointer instance, making it point at the same object that o was pointing to.

QExplicitlySharedDataPointer::~QExplicitlySharedDataPointer()

Decrements the reference count of the shared data object. If the reference count becomes 0, the shared data object is deleted. This is then destroyed.

[protected] T *QExplicitlySharedDataPointer::clone()

Creates and returns a deep copy of the current data. This function is called by detach() when the reference count is greater than 1 in order to create the new copy. This function uses the operator new and calls the copy constructor of the type T.

See QSharedDataPointer<T>::clone() for an explanation of how to use it.

[noexcept] const T *QExplicitlySharedDataPointer::constData() const

Returns a const pointer to the shared data object.

See also data().

[noexcept] T *QExplicitlySharedDataPointer::data() const

Returns a pointer to the shared data object.

void QExplicitlySharedDataPointer::detach()

If the shared data object's reference count is greater than 1, this function creates a deep copy of the shared data object and sets the d pointer of this to the copy.

Because QExplicitlySharedDataPointer does not do the automatic copy on write operations that members of QSharedDataPointer do, detach() is not called automatically anywhere in the member functions of this class. If you find that you are calling detach() everywhere in your code, consider using QSharedDataPointer instead.

[noexcept, since 6.0] T *QExplicitlySharedDataPointer::get() const

Same as data(). This function is provided for STL compatibility.

This function was introduced in Qt 6.0.

[noexcept, since 6.0] void QExplicitlySharedDataPointer::reset(T *ptr = nullptr)

Sets the d pointer of this to ptr and increments ptr's reference count if ptr is not nullptr. The reference count of the old shared data object is decremented, and the object deleted if the reference count reaches 0.

This function was introduced in Qt 6.0.

[noexcept] void QExplicitlySharedDataPointer::swap(QExplicitlySharedDataPointer<T> &other)

Swaps this explicitly-shared data pointer with other. This operation is very fast and never fails.

[noexcept] T *QExplicitlySharedDataPointer::take()

Returns a pointer to the shared object, and resets this to be nullptr. (That is, this function sets the d pointer of this to nullptr.)

[noexcept] bool QExplicitlySharedDataPointer::operator bool() const

Returns true if the d pointer of this is not null.

[noexcept] bool QExplicitlySharedDataPointer::operator!() const

Returns true if the d pointer of this is nullptr.

T &QExplicitlySharedDataPointer::operator*() const

Provides access to the shared data object's members.

[noexcept] T *QExplicitlySharedDataPointer::operator->()

Provides access to the shared data object's members.

[noexcept] T *QExplicitlySharedDataPointer::operator->() const

Provides const access to the shared data object's members.

[noexcept] QExplicitlySharedDataPointer<T> &QExplicitlySharedDataPointer::operator=(QExplicitlySharedDataPointer<T> &&other)

Move-assigns other to this QExplicitlySharedDataPointer instance.

[noexcept] QExplicitlySharedDataPointer<T> &QExplicitlySharedDataPointer::operator=(T *o)

Sets the d pointer of this to o and increments o's reference count. The reference count of the old shared data object of this is decremented. If the reference count of the old shared data object becomes 0, the old shared data object is deleted.

[noexcept] QExplicitlySharedDataPointer<T> &QExplicitlySharedDataPointer::operator=(const QExplicitlySharedDataPointer<T> &o)

Sets the d pointer of this to the d pointer of o and increments the reference count of the shared data object. The reference count of the old shared data object of this is decremented. If the reference count of the old shared data object becomes 0, the old shared data object is deleted.