QSHAREDPOINTER CAST EXAMPLE

QSharedPointer casting Qt Code: This function is suitable for use in if-constructs , like: If ptr2 ‘s template parameter is not a base or a derived type from ptr1 ‘s, you will get a compiler error. By fsmoke in forum Newbie. The scope of the pointer clearly shows the lifetime and ownership of the referenced object. Even though QWeakPointer tracks a pointer, it should not be considered a pointer itself, since it doesn’t guarantee that the pointed object remains valid. It is similar to std::

If you have any problems with the registration process or your account login, please contact us. QObject -derived classes can only be deleted in the thread they have affinity to which is the thread they were created in or moved to, using QObject:: Documentation sources may be obtained from www. Note, however, that the pointer tracking feature has limitations on multiple- or virtual-inheritance that is, in cases where two different pointer addresses can refer to the same object. Please ask Qt related questions on the forum and not using private messages or visitor messages. The pointer referenced by this object will not be deleted.

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QWeakPointer Class Reference

In silico In silico It is ok to obtain the value of the pointer and using that value itself, like for example in debugging statements:. Returns true if the pointer referenced by ptr1 is the same pointer as that referenced by ptr2.

This class is useful when an object needs to be heap allocated and deleted, but no more. Powered by vBulletin Version 4. Note that X must have the same cv-qualifiers const and volatile that Edample has, or the code will fail to compile.

The scope of the pointer clearly shows the lifetime and ownership of the referenced object. QObject -derived classes examp,e only be deleted in the thread they have affinity to which is the thread they were created in or moved to, using QObject:: It behaves exactly like a normal pointer for normal purposes, including respect for constness.

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QScopedPointer is lightweight, it makes no use of additional structure or reference counting.

QSharedPointer casting

Therefore, to access the pointer that QWeakPointer is tracking, you must first promote it to QSharedPointer and verify if the resulting object is null or not. The current pointer reference is discarded but is not deleted. Results 1 to exapmle of 2. Use qSharedPointerConstCast to cast away the constness.

The const and volatile differences between T and X are ignored. QSharedPointer will delete the pointer it is holding when it goes out of scope, provided no other QSharedPointer objects are referencing it. It is safe to use this feature even with code compiled without the feature. All functions in this class are reentrant. This allows one to catch mistakes like assigning the same pointer to two QSharedPointer objects.

Creates a QSharedPointer that points qsharedpointeg ptr. This class can, therefore, detach based on the type of access made to the data being guarded: The custom deleter is called when the strong reference count drops to 0 instead of the operator delete. The other object is converted first to a strong reference. Qsharedpoitner ptr2 ‘s template parameter is not a base or a derived type from ptr1 ‘s, you will examle a compiler error.

The const and volatile differences between T and X are ignored.

They are incompatible with one another, since each has its very different use case. Sign up or log in Sign up using Google.

If each row is represented by a DataObjectwhich could exist in more than one DataObjectTableModelby using reference-counted pointers, the table can clean up the DataObject s when it has the last shared pointer to the object. Donnez-nous votre avis 10 Adieu qmake, bienvenue qbs: Note that X must have the same cv-qualifiers qsharfdpointer and volatile qsharespointer T has, or the code will fail to compile. Returns true if this object is null. This class was introduced in Qt 4. Documentation sources may be obtained from www.

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For example, the following code promotes a QWeakPointer that was held to a strong reference and, if it succeeded, it prints the value of the integer that was held: This function is only available if the template type T is QObject or derives from it.

Your biological and technological distinctiveness will be added to our own. This is useful, for instance, for calling deleteLater in a QObject instead: If ptr2 ‘s type is not a base or a derived type from this ptr1 ‘s, you will get a compiler error. This is useful, for instance, for calling deleteLater in a QObject instead:.

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QSharedPointer guarantees that the object isn’t deleted, so if you obtain a non-null object, you may use the pointer. Optional pointer tracking A feature of QSharedPointer ecample can be enabled at compile-time for debugging purposes is a pointer tracking mechanism.

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