Memory management in Qt?

by

If you build your own hierarchy with QObjects, that is, you initialise all newly created QObjects with a parent,

QObject* parent = new QObject();
QObject* child = new QObject(parent);

then it is enough to delete the parent, because the parents destructor will take care of destroying child. (It does this by issuing signals, so it is safe even when you delete child manually before the parent.)

You could also delete the child first, the order doesn’t matter. For an example where the order does matter here’s the documentation about object trees.

If your MyClass is not a child of QObject, you’ll have to use the plain C++ way of doing things.

Also, note that the parent–child hierarchy of QObjects is generally independent of the hierarchy of the C++ class hierarchy/inheritance tree. That means, that an assigned child does not need to be a direct subclass of it’s parent. Any (subclass of) QObject will suffice.

There might be some constraints imposed by the constructors for other reasons, however; such as in QWidget(QWidget* parent=0), where the parent must be another QWidget, due to e.g. visibility flags and because you’d do some basic layout that way; but for Qt’s hierarchy system in general, you are allowed to have any QObject as a parent.

More Related Contents:

  1. memory layout C++ objects [closed]
  2. Create new C++ object at specific memory address?
  3. Decompile qt exe [closed]
  4. Qt Linker Error: “undefined reference to vtable” [duplicate]
  5. How to link opencv in QtCreator and use Qt library
  6. How to execute a functor or a lambda in a given thread in Qt, GCD-style?
  7. Q_OBJECT throwing ‘undefined reference to vtable’ error [duplicate]
  8. Stack Memory vs Heap Memory [duplicate]
  9. What does the “lock” instruction mean in x86 assembly?
  10. Why do compilers allow string literals not to be const?
  11. Declare abstract signal in interface class
  12. QString to char* conversion
  13. How do you determine the size of an object in C++?
  14. What are uses of the C++ construct “placement new”?
  15. QObject Multiple Inheritance
  16. Dark transparent layer over a QMainWindow in Qt
  17. Multithreaded Memory Allocators for C/C++
  18. Where are member functions stored for an object?
  19. how to restart my own qt application?
  20. Is there an intra-process local pipe in Qt?
  21. How can i estimate memory usage of std::map?
  22. Ncurses and Qt Interoperability
  23. QDialog exec() and getting result value
  24. How do I make an image resize to scale in Qt?
  25. how to add zlib to an existing qt installation
  26. Qt macro keywords cause name collisions
  27. Can you allocate a very large single chunk of memory ( > 4GB ) in c or c++?
  28. Can undefined behavior erase the hard drive?
  29. How to determine if returned pointer is on the stack or heap
  30. C++ function called without object initialization

Leave a Comment