Hi everybody,

I will be asking some confirmations instead of questions simple because even as a python developer I do not have (any apparent at least) problem with the code examples below. I wanted to create this topic to have my understanding of pointers as concrete as possible. I think along with myself, many people can benefit it.

I will be given examples topic by topic, again, all codes below are compile(not sure leaks though). Here I go.

1. Pointers point
Yeah, we know that. However, if I delete a pointer which points to an object such as QGraphicsItem, it deletes that object.

Qt Code: 
  1. QList <QGraphicsItem*> items = this->graphScene->items();
  2. foreach(QGraphicsItem *i, items)
  3. {
  4. 	MyGraphItem *graphItem = qgraphicsitem_cast< MyGraphItem *>(i);
  5. 	// I did stuff with graphItem here now it’s time to delete it
  6.         // not the object it points to though
  7. }
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If I delete it like this;

Qt Code: 
  1. delete graphItem;
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it deletes the graph item it points to. I just want to delete (remove from the memory) graphItem. Not the item it points to. So I am deleting it like this;

Qt Code: 
  1. graphItem = NULL;
  2. delete graphItem;
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I was wondering whether this way is the right way to delete the pointer while not touching the object it points to.



2. Returning Pointers
Is the approach I am using below a right one?
Qt Code: 
  1. MyGraphItem  *GraphView::getItem(const QString &name)
  2. {
  3.     QList <QGraphicsItem*> items = this->graphScene->items();
  4.     if(items.isEmpty())
  5.         return NULL;
  6.  
  7.     foreach(QGraphicsItem *i, items)
  8.     {
  9. 		// Here i am allocating memory
  10.         MyGraphItem  *graphItem  = qgraphicsitem_cast<MyGraphItem *>(i);
  11.         if(typeid(*graphItem ) == typeid(MyGraphItem ))
  12.         {
  13. 			// this is the object I want so return it
  14.             if(graphItem ->name == name)
  15.             {
  16.                 return graphItem ;
  17.             }
  18.         }
  19. 		// Hovewer if the object *graphItem is not wat I wanted
  20. 		// Should I delete it here, like so
  21. 		graphItem = NULL;
  22. 		delete graphItem;
  23.     }
  24.     return NULL;
  25. }
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What about the returning a string below. I assume the receiving method should delete the pointer when it's no longer needed, right?
Qt Code: 
  1. QString *GraphAttribute::getItemName()
  2. {
  3.     MyGraphItem *graphItem = qgraphicsitem_cast<MyGraphItem *>(this->parentItem());
  4.     return &graphItem ->name;
  5. }
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Another confirmation for returning pointer.

Qt Code: 
  1. GraphData *GraphItem::getAttribute(const QString &dataName)
  2. {
  3. 	// Here I have a QList that contains pointers of GraphData instances
  4.     if(this->data.isEmpty())
  5.         return NULL;
  6.  
  7.     foreach(GraphData *d, this->data) // Getting them individually
  8.     {
  9.         if(d->data.name == dataName) 
  10.             return attr; // This is what I want, return it, this return pointer must be deleted 
  11. 			// in caller method when it's no longer needed, right.
  12.         else
  13.         {
  14. 			// This is not what I want delete it
  15.             d = NULL;
  16.             delete d;
  17.         }
  18.     }
  19.     return false;
  20. }
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Would you please let me know if you see any problem in my code?

Thanks