Do not call Destroy directly in an application. The destructor is called automatically by the dataset that owns the object field component, and applications never need to call it explicitly. 

If an application creates a descendant of TObjectField without an owner, it should call Free instead of Destroy. Free checks that the field reference is not nil, and only then calls Destroy. 

Destroy closes the dataset, deletes the instance of TObjectField from the dataset, and calls the inherited destructor. 

System::TObject::Free