Re: How to test object hierarchy

[Georg Bauhaus <sb463ba@l1-hrz.uni-duisburg.de>]

Dmitry A. Kazakov <mailbox@dmitry-kazakov.de> wrote:
: type Derived_Object is new Root_Object with ...;
: procedure Test_Hierarchy
: (  Obj1 : in Derived_Object;
:   Obj2 : in Root_Object'Class;
:   Recursion : Boolean := False
: )  is
: begin
:   if Recursion
:      or else Obj2 not in Derived_Object'Class
:      or else Obj2 in Derived_Object
:   then
:      Do_It (Obj1, Obj2); -- Deal with Obj1 :>= Obj2
:   else
:      Test_Hierarchy (Obj2, Obj1, True); -- Dispatch again
:   end if;
: end Test_Hierarchy;
: 
: You have to override Test_Hierarchy for each new type, but I suppose that
: "do something" in your code is dispatching anyway. When Test_Hierarchy is
: not commutative it gets a bit more complicated, but I think you have got
: the idea.

Whenever I see an "if" testing for types I'm wondering whether
these ifs should be turned "to the outside" into what they mean
in the solution domain, but using language means. Is it really
advantageous or necessary to have to do manual dispatching in
your program?

And I have the same question that Hyman has asked about generics,
plus, should "with type" be mentioned in this context?


-- Georg