Re: Enforcing initialization protocol for protected type

[Georg Bauhaus <rm.dash-bauhaus@futureapps.de>]

Maciej Sobczak schrieb:
> Consider the Needs_Constructor type from the code example in the Ada
> wikibook:
> 
> http://en.wikibooks.org/wiki/Ada_Programming/Types/limited#Initialisi...
> 
> Is it possible to ensure a given initialization protocol for protected
> types as well?

The following is not using, I guess, your original
idea directly.  But it requires that the a proper context
be set up.  Then, the PO will initialize itself from
the context.  Context is passed in via known discriminants:

   -- method A, function pointer



   type Status_A is private;
   type A_Maker is access function return Status_A;

   -- method B, O-O construction



   type Status_B is private;
   package OO is
      type B_Maker is tagged private;

      function Make_B(Context: B_Maker) return Status_B;
   private
      type B_Maker is tagged record
         null;
      end record;
   end OO;

   type B_Maker_Ref is access OO.B_Maker'Class;

   protected type PO
     (First_A : not null A_Maker;
      First_B : not null B_Maker_Ref)
   is
      entry One;
      entry Two;
   private
      Data_A: Status_A := First_A.all;
      Data_B: Status_B := First_B.Make_B;
   end PO;