Re: Asyncronous message handling
Re: Asyncronous message handling
- Subject: Re: Asyncronous message handling
- From: "Mohan Parthasarathy" <email@hidden>
- Date: Wed, 7 Jan 2009 09:44:04 -0800
On Tue, Jan 6, 2009 at 8:12 PM, Keary Suska <email@hidden>wrote:
>
> On Jan 6, 2009, at 11:14 AM, Mohan Parthasarathy wrote:
>
> Let us say that there are two objects A and B.
>>
>> 1) Object A produces some data
>> 2) Object B consumes the data produced by object A
>>
>> When object B sends a message to object A for fetching the data, the data
>> is
>> not available immediately. When the data arrives later, it needs to notify
>> object B.
>>
>> For example, object A fetches data from some web service and Object B is
>> some sort of a "controller". How does one handle this in Cocoa ?
>>
>> - I can include the functionality of Object A within Object B itself and
>> hence there is no issue. But i guess this is prohibited as per the MVC
>> design.
>> - Object A can retain object B and later send the message back when data
>> is
>> available. But then this creates a dependency of object B knowing object
>> A
>> and object A knowing object B. Is this okay ?
>> - Any other way ?
>>
>
>
> NSNotificationCenter? Object Delegation Pattern <
> http://developer.apple.com/documentation/Cocoa/Conceptual/CocoaFundamentals/CommunicatingWithObjects/chapter_6_section_4.html#//apple_ref/doc/uid/TP40002974-CH7-SW26>
> ? Key-Value Observation?
>
Thanks for your response. I did look at Delegation but perhaps confused
because i thought object A also has to know about object B which i guess is
not needed. Is the following right understanding ?
object A has a method: -(void)fetchData:(id)sender
and also looks for a delegate in object B:
[sender respondsToSelector:@DataReady]
object B sends a message to object A: fetchData:(id)self
and implements DataReady
This way object A need not know anything about object B i guess.
Isn't Notification mechanism used for one-to-many ?
Thanks
mohan
>
> HTH,
>
> Keary Suska
> Esoteritech, Inc.
> "Demystifying technology for your home or business"
>
>
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