Problems with Distributed Objects
Problems with Distributed Objects
- Subject: Problems with Distributed Objects
- From: Andreas Mayer <email@hidden>
- Date: Wed, 25 Feb 2004 11:53:00 +0100
Hi all.
Since I'm not sure what my problem is (understanding or limitation of
DO or a bug in my code) I'll first explain what I am trying to achive.
I want a client connect to a server and hand over an NSImage (actually
a custom object that has an NSImage instance variable) for drawing in
the server's context.
What _is_ working: Connecting to the server and handing over an object
as reference (NSDistantObject).
What is _not_ working: Actually drawing the image and/or getting a copy
(instead of a reference) of the object holding the image.
And this is what I have done:
- created a framework that holds my custom class(es)
- imported this framework in the server and the client
- defined a protocol for the server
From the protocol:
@protocol AMTiggerServerProtocol
- (oneway void)addSign:(bycopy in AMTickerSign *)aSign;
Server declaration:
@interface AMTiggerServer : NSObject <AMTiggerServerProtocol> {
In the client:
id theServer;
theServer = [NSConnection
rootProxyForConnectionWithRegisteredName:@"AMTiggerServer" host:nil];
if (theServer) {
NSLog(@"connection established");
[theServer setProtocolForProxy:@protocol(AMTiggerServerProtocol)];
The implementation in the server (with debugging code):
- (void)addSign:(AMTickerSign *)aSign
{
[tickerView addSign:aSign];
NSLog(@"add sign with size: %f %f", [aSign size].width, [aSign
size].height);
if ([aSign respondsToSelector:@selector(image)]) {
NSImage *theImage = [[aSign image] copy];
if (theImage) {
[imageView setImage:theImage];
NSLog(@"image: %@", theImage);
NSLog(@"---");
} else {
NSLog(@"no image?!");
}
} else {
NSLog(@"does not respond to image");
}
}
The size ([aSign size]) is correct. As a look with the debugger shows,
I got an NSDistantObject. Why? I asked for a copy in the protocol. Do I
need to implement any special methods in my class for bycopy to work? I
implemented the NSCopying and the NSCoding protocols neither of which
seem to be used.
After the NSLog(@"image: %@", theImage); (which works) the app crashes
with a SIGBUS when releasing the autorelease pool. Why? Without this
NSLog statement there is no crash.
The copy (NSImage *theImage = [[aSign image] copy];) does not help. I
get a copy of the NSDistantObject. Is there a way to get the actual
data of the object in question? I guess I could use NSArchiver ...
Besides my problem of getting a local copy - why does the drawing not
work?
The AMTickerSign class implements
- (void)drawAtPoint:(NSPoint)point;
{
[image dissolveToPoint:point fraction:1.0];
}
When I send this message to my NSDistantObject, the method gets
executed but nothing is drawn. Why?
(Drawing works when using an object from a plugin instead of the one
from a remote client, so there shouldn't be a problem with the drawing
code.)
I'm totally out of ideas right now, so any help would be greatly
appreciated.
Regards, Andreas
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