Re: Using interfaces

[Jere <jhb.chat@gmail.com>]

On Saturday, June 2, 2018 at 11:20:53 AM UTC-4, gautier...@hotmail.com wrote:
> Hello,
> I am developing a package for displaying some kinds of figures on an open set of devices. I'm trying to use interfaces for that. 
> 
> SNIPPED...
>
> this is okay but I would need to copy-paste the same implementation code of Filled_Rectangle for device X in the case of Figure_B and so on. Not nice!
> 
> How do I get something like Figure_A_on_Device_X ?
> Am I expecting too much from interfaces?
> 

I generally do something similar to what you do in Rust:

      type Figure_A_on_Device_X is new Figure_A and Any_Device with record
         Device_Impl : Device_X;
      end record;
      procedure Filled_Rectangle (device: Figure_A_on_Device_X);

and then

      procedure Filled_Rectangle (device: Figure_A_on_Device_X) is
      begin
         device.Device_Impl.Filled_Rectangle;
      end Filled_Rectangle;

You can also make Figure_A_on_Device_X a private type to hide that.