Re: Sending object between threads.

FROM : Jorge Monteiro
DATE : Tue May 13 03:46:50 2003

Terry,

You need to implement the NSCopying and NSCoding protocols on all the
objects you want to pass. This will work within the same app or across
apps - using real DO.
Also remember if you pass the object pointer, like suggested before,
you should use an NSLock to lock access to the object so that the 2
threads do not access the object at the same time - if that happens the
app will crash and this problem will be very hard to track later on.

Regards,

Jorge Monteiro
http://www.jomosoft.com



On Thursday, January 23, 2003, at 05:23 AM, Terry Smyth wrote:

> Thanks Nico & Jake,
>
> That did the trick. By casting to a uintptr_t I can now see my object
> at the other end of the connection. Though I still don't understand
> why my objects are not getting encoded and transferred as I had
> expected (it seems at present just a pointer to the object is sent).
> This is fine for now while I am communicating between threads in the
> same app. Later, my worker thread will need to run on a separate
> machine, and I will need a full DO implementation - hopefully once
> I've done that, I will see my objects encoded and transferred across
> the connection.
>
> Thanks for your help,
>
> Terry
>
> On Tuesday, January 21, 2003, at 08:12  pm, Nico wrote:
>

>> Hi Terry!
>>
>> I also ran into this problem.
>> The simplest way to solve that problem is to pass your
>> object pointer castet to a uintptr_t.
>> After received by the worker thread simply cast the
>> pointer back.
>> Make sure the object is still valid for the worker.
>> Maybe you retain the object for the worker and the
>> worker releases it.
>>
>> Hope that helps...
>>     Nico
>>
>> On Montag, Januar 20, 2003, at 07:05  Uhr, cocoa-dev-
>> <email_removed> wrote:
>>

>>> Date: Mon, 20 Jan 2003 17:50:39 +0000
>>> Subject: Sending object between threads.
>>> From: Terry Smyth <terry.<email_removed>>
>>> To: <email_removed>
>>>
>>> Hi,
>>>
>>> Following the example given in the Cocoa documentation "Forming
>>> Connections Between Threads", I have implemented a separate thread in
>>> my app to do some stuff, using NSConnection/NSPort to communicate
>>> between the main thread and the worker thread. It all works, except
>>> that I'm having trouble passing my own custom objects to and from the
>>> worker thread (so I can't actually get my worker to do any useful
>>> work!!). I can pass other cocoa objects (eg NSString) just fine, and
>>> they appear intact at the other side of the connection. If I pass my
>>> own object, I just get junk at the other end.
>>>
>>> Objects of my custom class conform to NSCoding, but my
>>> encodeWithCoder:
>>> and initWithCoder: methods never get called. Have I missed something
>>> obvious here, or is it more likely a dumb coding bug? I'm going round
>>> in circles reading the documentation, but can't see what I'm doing
>>> wrong. Can anyone suggest what I might have missed, or where I can go
>>> for further reading (better still, is there any sample code which
>>> does
>>> this - I couldn't find any?)

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