Re: Experimenting with the OOP features in Ada

[Brian Drummond <brian@shapes.demon.co.uk>]

On Mon, 02 Jan 2017 08:27:44 -0800, Laurent wrote:

> On Monday, 2 January 2017 15:44:57 UTC+1, Brian Drummond  wrote:
>> So the
>> following are equivalent:
>> 
>> Test_Antibiotic := Base_Types.Antibiotics.Create_Code_SIL (
>>                              This => Test_Antibiotic, Code_SIL => "Test
>>                              Antibiotic 3")
>> 
>> Test_Antibiotic := Test_Antibiotic.Create_Code_SIL
>>                             (Code_SIL => "Test Antibiotic 3");
>> 
>> but the preferred form would be
>> 
>> Test_Antibiotic.Set_Code_SIL (Code_SIL => "gen");
>> 
>> -- Brian
> 
> Yes last one looks nice but doesn't work. No selector... Object is
> private.
> So 2nd one.
> Now I won't compile because Base_Types.Object is abstract. So I have to
> figure out how/where to put the overriding works. In John Barnes Book it
> looks so easy and light. Doing it myself feels clumsy


I recommend learning how to make the nicest looking one work; my 
procedure was a first pass at guidance, not a complete solution.

Procedure Set_Code_SIL (This : in out Base_Types.Antibiotics.Objects;
                        Code_SIL => "gen");

Where did you put this procedure?

As Dmitry says, you need to provide setters if you're manipulating parts 
of an object, so this procedure, a setter, should be part of the 
Base_Types.Antibiotics package (with implementation in its body) so that 
it has access to the private part, where the components are declared.

The error message fragment (without file:location) you report suggests it 
was probably somewhere else.

-- Brian