Object-oriented Software in Ada 95

282 Persistence
19.1.1 Putting it all together
When compiled with the class Tel_list and the package Pack_types an example interaction using the
program would be as follows:
=UK
-- Previously stored
IDC for UK is 44
New Zealand 64 -- Add IDC for New Zealand
Sweden 46 -- Add IDC for Sweden
Portugal 3510 -- Invalid IDC
=Portugal -- Lookup IDC for Portugal
IDC for Portugal is 3510
Portugal 351 -- Try to add new IDC for Portugal
Name already in directory
*Portugal 351 -- Correct invalid IDC
=Portugal -- Lookup IDC for Portugal
IDC for Portugal is +351
Note:
The user’s input is indicated by bold type.
The actions allowed are:
+ Add country and IDC to collection
= Extract IDC for country
* Change IDC for existing country
19.1.2 Setting up the persistent object
The following program creates the initial persistent collection:
with Ada.Text_Io, Class_Tel_List;
use Ada.Text_Io, Class_Tel_List;
procedure Main is
Tel_List : Pic;
begin
Put("Creating Telephone list"); New_Line;
Set_Name( Tel_List, "tel_list.per" );
Add( Tel_List, "Canada ", "+1 " );
Add( Tel_List, "USA ", "+1 " );
Add( Tel_List, "Netherlands ", "+31 " );
Add( Tel_List, "Belgium ", "+32 " );
Add( Tel_List, "France ", "+33 " );
Add( Tel_List, "Gibraltar ", "+350 " );
Add( Tel_List, "Ireland ", "+353 " );
Add( Tel_List, "Switzerland ", "+41 " );
Add( Tel_List, "UK ", "+44 " );
Add( Tel_List, "Denmark ", "+45 " );
Add( Tel_List, "Norway ", "+47 " );
Add( Tel_List, "Germany ", "+49 " );
Add( Tel_List, "Australia ", "+61 " );
Add( Tel_List, "Japan ", "+81 " );
end Main;
19.2 The class PIC
The class Pic (Persistent Indexed Collection) implements an indexed collection as a binary tree. An identity is
given to an instance of the class PIC so that when the object’s life-time ends, its state will be saved to disk. The
file name used to save the state is the object’s identity.
The specification for the class PIC is as follows:
© M A Smith - May not be reproduced without permission