Re: problem with abstract types

[Ulrich Eckhardt <uli.e@gmx.de>]

John English wrote:
> Ulrich Eckhardt wrote:
> 
>>procedure main is
>>    reg : registry_Access;
>>    err : r_error;
>>begin
>>    reg := getRegistry(CLASS_USER,To_Unbounded_String("registrytest"));
>>    openRegistry(reg'access,err);

> Reg is already an access value; you don't need to use 'Access
> at all here. I think you'll find that this works:
>     openRegistry(reg,err);
> 
No. openRegistry is first defined abstract and then implemented
as openRegistry(reg : in out file_registry; ..) and
openRegistry(reg : in out win_registry; ..) .

getRegistry should instantiate a class of file_registry or
win_registry depending on the Operation System and returns
this to the main programm. Within the main programm now
the correct instances of openRegistry should be choosen, so
that the current used implementation is not visible.
So the programmer which uses the registry package shouldnt't
care (and shouldn't see) whats behind the scene.

Uli
-- 
Ulrich Eckhardt
http://www.uli-eckhardt.de