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)
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