QList question

[stevey]

Instead of

private:
  QList<structOrder> m_Orders;

private:
  QList<structOrder> m_Orders;

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use

private:
  QList<structOrder>* m_Orders;

private:
  QList<structOrder>* m_Orders;

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The are certain key things you need to be aware of with C++.
One very important thing is that when you call return at the end of the function, a COPY of the type you're returning is created to hold the data. This is because any variable declared inside a function is a STACK variable for the scope of that function. So if you declare a non pointer variable then return it, in your case in the call to orders(), you've essentially chained your call to .append(tmpOrder) on a copy of the variable that is lost as soon as the next line is called.

Now by declaring a QList<structOrder>*, at the end of your function you'll be returning a COPY still, but it will be a copy of a POINTER. The actual instantiated QList is on the heap so isn't cleaned up at the end of the function, therefore copied QList*'s data you'll be appending to is valid and won't get lost in transit.

In terms of architecture, you might want to re-consider this kind of thing anyway and use a wrapper function. A sideline of hiding the QList also is that you could schtick with your non pointer version:

void ShoppingCartView::AddOrder(structOrder order)
{
  m_Orders.append( order );
}

void ShoppingCartView::AddOrder(structOrder order)
{
  m_Orders.append( order );
}

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