Re: Сreate attributes.

[Brad Moore <bmoore.ada@gmail.com>]

On Friday, December 21, 2018 at 10:37:14 PM UTC-7, eduards...@gmail.com wrote:
> Sorry for the stupid question...
> 
> For example. I have type:
> 
>    type Person is record
>       First_Name : Unbounded_String := Null_Unbounded_String;
>       Last_Name : Unbounded_String := Null_Unbounded_String;
>    end record;
> 
> There is a list:
> 
>    package People_Package is new  Ada.Containers.Vectors(Natural, Person);
>    People : People_Package.Vector;
> 
> Next, I want to display this list with headers:
> 
> ----------------------------
> |   NAME    |   SURNAME    |
> ----------------------------
> |   John    |    Smith     |
> |   Ada     |   Lovelace   |
> ...
> ----------------------------
> 
> Can I use attributes to display headers?
> For example something like this:
> 
> People'First_Name_Header
> 
> 
> How can this be implemented?

You could use a class-wide type or a type with discriminants such as;

   type Person_Attribute_Kinds is (Name, Surname);
   
   type Person_Attribute (Attribute_Name : Person_Attribute_Kinds
                          := Person_Attribute_Kinds'First) is
      record
         case Attribute_Name is
            when Name | Surname =>
               Name_String : Unbounded_String := Null_Unbounded_String;
         end case;
      end record;
      
      type Person is
         record
            First_Name : Person_Attribute(Name);
            Last_Name  : Person_Attribute(Surname);
         end record;
      
   X : Person;
begin
   Put_Line ("| " & X.First_Name.Attribute_Name'Image &
              " | " & X.Last_Name.Attribute_Name'Image & " |");