On Thu, Oct 30, 2008 at 1:52 PM, Andre Masse <[EMAIL PROTECTED]> wrote: > Hi, > > I'm currently developing an "in house" application which serves as a front > end to a PostgreSQL database. There will be only 4 users at maximum peak, so > this is a fairly small load for the database. At this point, I'm using > notifications to inform a particular form when a query result is ready to > process. Since each form has its own connection (a cocoa wrapper class to > libpq) I'm wondering if using delegation would be a better idea. Now, I may > move the querying stuff to its own thread at some point (when I get more > familiar to the cocoa way). > > I've read the net on how to implement a delegate in a custom class and it > works when in the same thread but, is delegation working in a threading > environment? In other words, can I call a delegate method from another > thread?
It's important to remember that "delegate" is just a design pattern, not a language feature. A delegate is just a defined set of messages that you send to an object in certain situations. When it comes to threads, they behave just like any other messages, because they are just regular messages. So what happens when you send a delegate message on a secondary thread? Same thing as when you send any other message: the corresponding method gets invoked synchronously on the same thread. (I.e. you call it directly.) This can be bad. If you're going to do this then your delegate needs to be prepared to receive delegate messages on secondary threads, and that can sometimes be annoying. Sometimes it's entirely reasonable. It really depends on your situation. If your situation is such that it's unreasonable, the solution is easy: just use performSelectorOnMainThread: to ship the delegate message back to the main thread where it can be invoked in a better place. If you want to invoke it on some thread other than the main thread then Cocoa provides a fair number of inter-thread communication techniques that you can use. Ignore the fact that this is a "delegate" and just see how and where you want to send your message. Mike _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to [EMAIL PROTECTED]
