Question

type
  TTest = class
    a: integer;
  end;
  TTest2 = class(TTest)
    b: integer;
  end;

  var c:TTest;

  begin
    c:=TTest2.Create();
    c.Free;
  end;

Answer 1

No, it will not.

A variable of a base class type can be used for instantiating objects from its child classes (they are type compatible), but take note that using such a variable, you will have access only to TTest members, not TTest2 members. That means; you can access “a”, but not “b”.

Also, if you face any exception during TTest2.Creation execution, Create won’t return a partially built object.

However, if you have some other codes between TTest2.Create and c.Free calls, raising an exception in those codes can cause memory leak; because C.Free might not execute. In such a case you should use a try-finally block.