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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: child class of limited_controlled not inheriting data
Date: Fri, 5 Aug 2016 21:37:58 +0200
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Date: 2016-08-05T21:37:58+02:00
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On 2016-08-05 20:59, b.mcguinness747@gmail.com wrote:
> I defined a base class as
>
>
> with Ada.Float_Text_IO;
> with Ada.Finalization;
>
> package sofa.time.two_part_date is
>   type Date is new Ada.Finalization.Limited_Controlled with private;
>
>   function To_Date (days : Integer; fraction : Real) return Date;
>   function To_Date (time_string : String)            return Date;
>
>   function "<"  (left, right : Date) return Boolean;
>   function "<=" (left, right : Date) return Boolean;
>   function "="  (left, right : Date) return Boolean;
>   function ">=" (left, right : Date) return Boolean;
>   function ">"  (left, right : Date) return Boolean;
>
>   procedure Add_Days (this : in out Date; days : in Integer; fraction : in Real);
>
>   function Get_Day_Count (this : Date)    return Integer;
>   function Get_Day_Fraction (this : Date) return Real;
>   function To_Real (this : Date)          return Real;
>   function To_String (this : Date)        return String;
>
> private
>   type Date is new Ada.Finalization.Limited_Controlled with record
>     day_count    : Integer;
>     day_fraction : Real;    -- Normalized to 0.0 <= x < 1.0
>   end record;
>
>   overriding procedure Initialize (this: in out Date);
>   overriding procedure Finalize   (this: in out Date);
>
>   procedure Normalize (day_count : in out Integer; day_fraction : in out Real);
> end;
>
> (It's Limited_Controlled because I want to force day_fraction to be
> normalized when objects of the class are created.)

It must be Controlled if some complicated initialization required, and 
likely abstract, not Limited_Controlled.

> Then I defined a child class as
>
> with sofa.time.two_part_date;
>
> package sofa.time.Julian_Day_Numbers is
[...]
> When I try to compile the child class, I get error messages such as
>
> sofa-time-julian_day_numbers.adb:77:79: "day_count" is not a
> component  of type "Julian_Day_Number" defined at sofa-time-julian_day_numbers.ads:4
>
> indicating that the child class is not inheriting the data from the parent class.
>
> What is wrong here?

You didn't make day_count visible. There are three ways to do it, in the 
order of publicity:

1. Make it a public member

2. Make it available through getter/setter. You have Get_Day_Count, if 
that is, then use it in Julian_Day_Numbers.

3. Make Julian_Day_Numbers child package:

    sofa.time.two_part_date.Julian_Day_Numbers


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