From: stefanmairhofer@gmx.at
Subject: Observer Pattern / Concurrency with ObjectAda
Date: Mon, 19 Nov 2007 03:07:34 -0800 (PST)
Date: 2007-11-19T03:07:34-08:00 [thread overview]
Message-ID: <07095dbf-53a4-4cdb-a3bc-3302b499b98d@e1g2000hsh.googlegroups.com> (raw)
Hello!
I'm currently working on a software-pattern based project with
ObjectAda and I would require to implement an Observer pattern for my
program.
I've stumbled upon an example of the "Observer Pattern with an
Concurrent Subject" from Matthew Heaney
http://www.adapower.com/index.php?Command=Class&ClassID=Patterns&CID=287
And I was not able to run it on ObjectAda 7.2.2. Embedded (I get
access-errors, constraint-errors and sometimes deadlocks). When I
tried the program using MinGW with gccada it worked perfectly.
Apparently the Attach and Detach functions do not work properly and in
the main procedure Test_Observers the Clock declaration results in an
Constraint_Error / access error
procedure Test_Observers is
Timer : aliased Clock_Timer;
Clock : Digital_Clock (Timer'Access); -- <-- Constraint_Error
begin
...
(little help : Timer = subject, which includes a task that informs the
observers via notify(),
Clock = observer, which has the update() method)
Any ideas why it works with GNAT, but not with ObjectAda?
Thank you for your help!
Best regards
Mairhofer Stefan
reply other threads:[~2007-11-19 11:07 UTC|newest]
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