I have a Delphi Form that provides the functionality behind an interface object that other parts of the code get references too via a property belonging to the Form. I can't delegate the interface functionality to a child object because too much of that functionality is serviced by controls/components on the form. I can't use TAggregatedObject or TContainedObject to link the lifetime of the interfaced objects being passed around to the Form because the TForm class does not inherit from TinterfacedObject and Delphi does not support multiple inheritance so I can't mix in TInterfacedObject into the inheritance chain. This situation can lead to access violations if a Form gets destroyed while some other code holds one of the interface references passed out by the Form. Can anyone think of a good solution to this problem?
You can delegate the interface to a child object, just have that object contain an internal pointer to the Form so it can access the Form's controls when needed, no different then you are already doing right now.
You can use TAggregateObject or TContainedObject for your needs. They do not require the Form to derive from TInterfacedObject. All they do require is an IInterface interface pointer, and TComponent derives from IInterface (and overrides the _AddRef() and _Release() to disable reference counting), so you can pass the Form itself (being a TComponent descendant) as the required IInterface pointer.
That leaves the only issue remaining - the Form closing while active interface references are being held by other code. The simpliest solution is to either 1) rewrite that code to not hold on to those references while the Form is closing, or 2) don't allow the Form to close until those references have been released.