Object-oriented Software in Ada 95

Polymorphism 235
16.5 A building information program
A class Building, which is used as a container to store and retrieve details about the accommodation in a
building, has the following responsibilities:
Method
Add
About
Responsibility
Add a description of a room.
Return a description of a specific room.
The Ada specification for the class Building is:
with Class_Room, Class_Room.Build;
use Class_Room, Class_Room.Build;
package Class_Building is
type Building is tagged private;
procedure Add( The:in out Building; Desc:in P_Room );
function About(The:in Building; No:in Positive) return String;
private
Max_Rooms : constant := 15;
type Rooms_Index is range 0 .. Max_Rooms;
subtype Rooms_Range is Rooms_Index range 1 .. Max_Rooms;
type Rooms_Array is array (Rooms_Range) of P_Room;
type Building is tagged record
Last : Rooms_Index := 0; --Last slot allocated
Description : Rooms_Array; --Rooms in building
end record;
end Class_Building;
The procedure Add adds new data to the next available position in the array.
package body Class_Building is
procedure Add( The:in out Building; Desc:in P_Room ) is
begin
if The.Last < Max_Rooms then
The.Last := The.Last + 1;
The.Description( The.Last ) := Desc;
else
raise Constraint_Error;
end if;
end Add;
Note:
The exception Constraint_Error is raised if there is no more free space in the array.
© M A Smith - May not be reproduced without permission