On Wed, Jul 7, 2010 at 3:46 PM, Brian Hurt <bhur...@gmail.com> wrote: > I'm wondering if the following pattern is safe or not. I'm in a > transaction, and I want to create an agent and then send it an initializing > message (the message function isn't transaction-safe, so I don't want to run > it in the transaction). So I want to do something like: > > (def my-ref (ref nil)) > > (defn example [ f ] > (dosync > (if (nil? @my-ref) > (let [ a (agent nil) ] > (ref-set my-ref a) > (send a init-function) > (send a f)) > (send @my-ref f)))) > > (actually, what I want to do is rather more complicated than this, but this > demonstrates the problem). So, my question is: is it guaranteed that > init-function will be received by the agent before any f functions are > received? > > Brian > > --
It's not guaranteed the init-function will complete before f. At the end of the Concurrency (Chapter 6) of Programming Clojure, Stuart Halloway outlines a rationale and a way to create functions that only run once. Related code can be found here - see 'runonce': http://github.com/stuarthalloway/lancet/blob/master/lancet.clj I hope that helps with what you're trying to do! Ryan -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
