Classwide Container

Classwide Container

[Yves Malette]

I am having trouble creating an array of  classes.....
that is the simplest way I can say it .... I have included a snippet of
code which can better explain my attempts.....


    type Base_Message_Rtype is tagged                       --base class

 record
     null;
 end record;

    type External_Message_Rtype is new Base_Message_Rtype with    --some
new class of message
 record
with their respective functions
     Sent_To : Send_Ptype := Send_Method'Access;
     Pending : Pending_Ptype := Pending_Method'Access;
 end record;

   type Message_Array_Rtype is
      array (Messages) of Base_Message_Rtype'Class;   -- an array that
can

contain message classes forever

as they become available...

the above example does'nt compile ( BASE_MESSAGE_RTYPE'CLASS must be
constrained )..
which I can agree with......

but I have spent three weeks with my trusty Cohen book and I know I can
constrain it by merely
turning my message_array component into a pointe..(oopss...access
type).....

type Node_Pointer_Type is access Base_Message_Rtype'Class;

type Message_Array_Rtype is
    array (Message_Etype) of Node_Pointer_Type;

this will compile, but unfortunately I can only access the methods from
my base class and not
the classwide access expected in the near future.......
              (Base_Message_Rtype'Class)

I trying create a simple classwide container............................
I am almost their...any help would
be appreciated

New Ada Guy ....

--
Thanks in advance.  Yves Bernard Malette   "Expect GREAT Things!"

"Disclaimer about my views and my employer goes here"

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Re: Classwide Container

[Dale Stanbrough]

Yves Malette writes...

"I am having trouble creating an array of  classes....."


	type Object is tagged null record;
	
	type Object_Ptr is access all Object'class;
	
	
	procedure Dispatch (Item : Object);
	
	
	type Object_Class_Array is array (Integer range <>) of Object_Ptr;
	
	
	
	type A is new Object with null record;
	
	procedure Dispatch (Item : A);
	
	etc.
	
	
	...
	   List : Object_Class_Array (1..3);
		
	begin
	   List (1) := new Object;
	   List (2) := new A;
	   List (3) := new B;
	   
	   
	   for i in List'range loop
	      Dispatch (List (i).all);
	   end loop;
	end;


Hope this helps...

Dale