Re: Delegates

FROM : Mike Abdullah
DATE : Mon May 19 23:16:19 2008

On 19 May 2008, at 21:23, I. Savant wrote:

> On Mon, May 19, 2008 at 2:54 PM, Michael Vannorsdel <<email_removed>
> > wrote:

>> There's nothing that guarantees a Cocoa delegate will act for 
>> another object
>> and that the represented object won't act how it wants as well. 
>> Sometimes a
>> delegate method is just a notification something happened/happening 
>> without
>> the delegate having any say on the matter or affect on the 
>> represented
>> object's course of action on that matter.

>
>  Yes, but the delegating object *always* follows this pattern:
>
> - I'm doing something for which I can ask a delegate for assistance or
> advice or in which the delegate might be interested, so ...
> - If I have a delegate ...
>  - If the delegate responds to this particular delegate message
>  - Send the message to the delegate and *wait for it to return* (ie,
> it's all within the same trip around the run loop, unlike
> notifications).


Um, that's wrong. To quote:

A notification center delivers notifications to observers 
synchronously. In other words, the postNotification:methods do not 
return until all observers have received and processed the 
notification. To send notifications asynchronously use 
NSNotificationQueue

Indeed, most -fooDidBar: style delegate methods are implemented via 
NSNotificationCenter. But of course that's just an implementation 
detail that probably doesn't matter to the OP.

Mike.