[Pharo-project] [COTDC] 40#2 - NonReentrantWeakMessageSend

laurent laffont laurent.laffont at gmail.com
Tue Apr 5 20:29:50 CEST 2011


Thanks a lot Henrik.

Laurent.

On Tue, Apr 5, 2011 at 12:02 PM, Henrik Johansen <
henrik.s.johansen at veloxit.no> wrote:

> NonReentrantWeakMessageSend does what it says, while the message is being
> executed, additional evaluations will be discarded.
> It's used by when:sendOnce:to: protocol from Polymorph events, but unused
> in the base image.
> when:send:to:exclusive: is used one place though.
>
> It's useful when objects are mutually registered to each other's events,
> but the actions may lead to the others action being triggered.
> Examples are
> - two lists whose contents update based on the selection in the other
> - The DiffMorph (Uses ExclusiveWeakMessageSend)
>
> ExclusiveWeakMessageSend are used when the decision whether to process an
> event is shared between multiple objects.
> IE 2 objects respond to different events, but if received simultaneously,
> only the first of them should have it's action executed.
>
> With Announcement, the corresponding functionality to non-reentrancy would
> be achieved using:
> VW - AnnouncementCollection>>suspendWhile:  anActionBlock
> Pharo - Announcer >> suspend: aSubscriber while: anActionBlock (As we
> neither have a specific AnnouncementCollection class, nor access to Registry
> itself. Not implemented yet though :P)
>
> The shared state required to achieve Exclusivity would probably have to
> recide outside of the framework.
>
> Cheers,
> Henry
>
>
> On Apr 4, 2011, at 9:59 56PM, laurent laffont wrote:
>
> Today:  NonReentrantWeakMessageSend
>
>
> (ExclusiveWeakMessageSend aborted - no answer)
>
>
> Comment Of The Day Contest - One Day One Comment
> Rules:
> #1: Each day a not commented class is elected. Each day the best comment
> will be integrated with name of the author(s).
> #2: If you cannot comment it, deprecate it.
> Results: http://code.google.com/p/pharo/wiki/CommentOfTheDayContest
>
> Laurent
>
>
>
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