1.8.5.2 A second example of multiple inheritance

Here is a further extension to the example in An example of multiple inheritance, with an additional interface i-foo-ex .that inherits from i-foo as in the following IDL:

[ uuid(7D9EB761-E4E5-11D5-BF02-000347024BE1) ]

interface IFooEx : IFoo

{

  HRESULT meth4();

}

This interface has the following additional implementations:

1. An implementation defining all the methods in i-foo-ex :

(define-com-implementation foo-ex-impl-1 ()

  ()

  (:interfaces i-foo-ex))

(define-com-method meth1 ((this foo-ex-impl-1))

  s_ok)

(define-com-method meth2 ((this foo-ex-impl-1))

  s_ok)

(define-com-method meth3 ((this foo-ex-impl-1))

  s_ok)

(define-com-method meth4 ((this foo-ex-impl-1))

  s_ok)

2. A combined implementation, inheriting from step 3 from An example of multiple inheritance and step 1 above.

(define-com-implementation foo-ex-impl-2 (foo-impl-12

                                          foo-ex-impl-1)

  ()

  (:interfaces i-foo-ex))

In step 2 , the class foo-ex-impl-2 implements the interface i-foo-ex and is a subclass of foo-ex-impl-1 , which implements i-foo . When the following form is evaluated with p-foo-ex created from an instance of foo-ex-impl-2 :

(let ((object (make-instance 'foo-ex-impl-2)))

  (with-temp-interface (p-foo-ex)

      (nth-value 1 (query-object-interface

                    foo-ex-impl-2

                    object

                    'i-foo-ex))

    (with-com-interface (call-p-foo i-foo-ex) p-foo-ex

      (values (call-p-foo meth1)

              (call-p-foo meth2)

              (call-p-foo meth3)

              (call-p-foo meth4)))))

the four values are S_OK , E_NOTIMPL , S_OK and S_OK .

Note that, even though foo-ex-impl-2 only explicitly implements i-foo-ex , the methods meth1 , meth2 and meth3 were declared in its parent interface i-foo . This means that their definitions (including the "unimplemented" definition of meth2 ) are inherited from foo-impl (via foo-impl-12 ), because foo-impl-12 is before foo-ex-impl-2 in the class precedence list of foo-ex-impl-2 . Only meth4 , which is declared in i-foo-ex , is inherited from foo-ex-impl-1 .