CODEWITHSUNDEEP
c++listqtpointersscene
Vadixem
Vadixem

Reputation: 99

Organizing items in QGraphicsScene

Is this a good practice to store graphic items of scene in lists? I know that QGraphicsItem has virtual method int type() and you can dynamically find items by type. So what I mean is that I want to store my graphic items on stack in separate lists.

class Scene : public QGraphicsScene
{
         public:
         // Constructors etc.
         private:
         // Store graphic items in lists by value
         QList<Carrot> m_carrots; 
         QList<Apple> m_apples;
};

This might sound dumb but the main concerns I have that in my current project everything is bound on using pointers and sometimes there are segmentation faults. And deleting items using 

delete item; 
item = nullptr;

And I want to manage items just using let's say m_apples.removeAt(index). The problem is I don't know yet what it can lead to, also the project is pretty huge, so these changes can affect other pieces of code and take a lot of time. But I think it might help in managing memory safer way. Thanks in advance

Upvotes: 0

Views: 353

Answers (1)

Kuba hasn&#39;t forgotten Monica
Kuba hasn&#39;t forgotten Monica

Reputation: 98505

If you store items by value, you must treat them as values and let the container manage the memory. An explicit delete on such an item is a bug. Qt's item classes are not copyable - thus you can:

  1. Make the derived classes copyable as QList has to copy.

  2. Use std::list as it doesn't need to copy.

  3. Use a vector of unique pointers, e.g. std::vector<std::unique_ptr>.

Upvotes: 0

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