Re: generic unit : compilation error ! please help me

Re: generic unit : compilation error ! please help me

[Stephen Leake]

nblanpain@hotmail.com writes:

> hello,
> When i compile the following programm, i have the following error on
> function Set_Unit_To_Test of class "child-test_unit.adb" :
> "14 : invalid tagged conversion, not compatible with type T_Child'Class
> defined at child.ads"
>  I don't undestand this error : please help me !
>
> ## parent.ads ## :

minor point; please use Ada comments for separators like this, so
gnatchop can handle them.

> generic
>    type T_Real is digits <>;
> package Parent is
>    type T_Parent is tagged private;
>    type T_Parent_Access is access all T_Parent;
> private
>    type T_Parent is tagged record
>       Real : T_Real;
>    end record;
> end Parent;

I have not fully sorted out your problem, because I find the names too
confusing. While it is proper to have similar names like this in a
finished product, they do get in the way of finding structural
problems.

So first, do these steps:

1) Get rid of the subtypes; use the full type names. It will make
   things clearer.

2) Name things clearly, without relying on the package name;
   Parent_Class_Access_Type, Child_Class_Access_Type.

I think you have too many class-wide access types. In particular, I
think you are trying to store a parent unit test in an object of type
child unit test. The object probably needs to be of type
Parent_Class_Access.

The clearer names will help you sort out what you really want to do.
Once that is clear, you can change the names back to be more
user-friendly. 

-- 
-- Stephe

Re: generic unit : compilation error ! please help me

[Dmitry A. Kazakov]

On 24 Feb 2006 01:19:47 -0800, nblanpain@hotmail.com wrote:

> ## parent.ads ## :
> generic
>    type T_Real is digits <>;
> package Parent is
>    type T_Parent is tagged private;
>    type T_Parent_Access is access all T_Parent;
> private
>    type T_Parent is tagged record
>       Real : T_Real;
>    end record;
> end Parent;
> 
> ## child.ads ##
> with Parent;
> generic
>    type T_Real is digits <>;
>    with package Par is new Parent (T_Real);
> package Child is
>    type T_Child is new Par.T_Parent with private;
>    type T_Child_Access is access all T_Child;
> private
>    type T_Child is new Par.T_Parent with record
>       Real2 : T_Real;
>    end record;
> end Child;
> 
> ## parent-test_unit.ads ##
> generic
> package Parent.Test_Unit is
>    subtype T_Unit_To_Test is Parent.T_Parent;
>    subtype T_Unit_To_Test_Access is Parent.T_Parent_Access;
>    type T_Unit_To_Test_Class_Access is access all T_Unit_To_Test'Class;
>    type T_Test_Unit is tagged private;
>    type T_Test_Unit_Access is access all T_Test_Unit;
>    procedure Set_Unit_To_Test
>      (This : in out T_Test_Unit;
>       Utt  : in T_Unit_To_Test_Class_Access);
> private
>    type T_Test_Unit is tagged record
>       Unit_To_Test : T_Unit_To_Test_Class_Access;
>    end record;
> end Parent.Test_Unit;
> 
> ## parent-test_unit.adb ##
> package body Parent.Test_Unit is
>    procedure Set_Unit_To_Test
>      (This : in out T_Test_Unit;
>       Utt  : in T_Unit_To_Test_Class_Access) is
>    begin
>       This.Unit_To_Test := Utt;
>    end Set_Unit_To_Test;
> end Parent.Test_Unit;
> 
> ## child-test_unit.ads ##
> with Parent.Test_Unit;
> generic
>    with package Parent_Test_Unit is new Parent.Test_Unit;

with package Parent_Test_Unit is new Par.Test_Unit;

Parent of Child and Parent of Parent.Test_Unit should be the same beast.

> package Child.Test_Unit is
>    subtype T_Unit_To_Test is Child.T_Child;
>    subtype T_Unit_To_Test_Access is Child.T_Child_Access;
>    type T_Unit_To_Test_Class_Access is access all T_Unit_To_Test'Class;
>    type T_Test_Unit is new Parent_Test_Unit.T_Test_Unit with private;
>    type T_Test_Unit_Access is access all T_Test_Unit;
>    procedure Set_Unit_To_Test
>      (This : in out T_Test_Unit;
>       Utt  : in T_Unit_To_Test_Class_Access);
> private
>    type T_Test_Unit is new Parent_Test_Unit.T_Test_Unit with record
>       Unit_To_Test2 : T_Unit_To_Test_Class_Access;
>    end record;
> end Child.Test_Unit;
> 
> ## child-test_unit.adb ##
> package body Child.Test_Unit is
>    procedure Set_Unit_To_Test
>      (This : in out T_Test_Unit;
>       Utt  : in T_Unit_To_Test_Class_Access) is
>    begin
>       Parent_Test_Unit.Set_Unit_To_Test
>         (Parent_Test_Unit.T_Test_Unit (This),
>          Parent_Test_Unit.T_Unit_To_Test_Class_Access (Utt));    --
> error !!!!!!!
>       This.Unit_To_Test2 := Utt;
>    end Set_Unit_To_Test;
> end Child.Test_Unit;

P.S. Don't use pointers, generics and Hungarian notation.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de