Sending object between threads.
Sending object between threads.
- Subject: Sending object between threads.
- From: Terry Smyth <email@hidden>
- Date: Mon, 20 Jan 2003 17:50:39 +0000
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?)
Here's what my custom object looks like:
@interface ChangerRequest : NSObject <NSCoding>
{
unsigned long requestID;
RequestType type;
BOOL isRunning;
}
@end
@implementation ChangerRequest
- (id)init
{
requestID = INVALID_REQUEST_ID;
isRunning = NO;
return self;
}
- (void) encodeWithCoder: (NSCoder *)coder
{
[coder encodeValueOfObjCType: @encode (unsigned long) at:
&requestID];
[coder encodeValueOfObjCType: @encode (RequestType) at: &type];
[coder encodeValueOfObjCType: @encode (BOOL) at: &isRunning];
}
- (id) initWithCoder: (NSCoder *)coder
{
// Must decode keys in same order as encodeWithCoder:
[coder decodeValueOfObjCType: @encode (unsigned long) at:
&requestID];
[coder decodeValueOfObjCType: @encode (RequestType) at: &type];
[coder decodeValueOfObjCType: @encode (BOOL) at: &isRunning];
return self;
}
and my call to the worker thread looks like this:
// Allocate and initialise a new request.
ChangerRequest *theRequest = [[ChangerRequest alloc] init];
[theRequest setCaller: (id)0x98765]; // Some junk just to see it
working.
[theRequest setType: fourth_type];
[requests addObject: theRequest]; // maintain a list of outstanding
requests.
// Now send the request to the server to be actioned.
[requestServer newRequestFromClient: theRequest];
where requestServer was set up in method setServer (as described in the
documentation), and the function newRequestFromClient is defined in a
protocol as follows:-
@protocol RequestHandlerServerMethods
- (void) newRequestFromClient: (ChangerRequest *) theRequest;
@end
Any help very much appreciated,
Terry Smyth
SGL
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