Why TForm.Handle is a getter instead of a field?

Question

I was debugging a complicated bug recently. It was caused by accessing a non-existing Form.Handle (garbaged pointer). The bug revealed itself in rather unexpect

Answer 1

The form object can exist even when the underlying OS window doesn't. During those times, the Handle field would be 0, which isn't helpful to code that needs a valid window handle. To ensure you get a valid handle each time you need one, you'd need to call HandleNeeded prior to referring to the Handle field. As a property with a getter, the property can call HandleNeeded for you automatically, making it easier to use the Handle property.