Working with Notifications and NSFileHandle

FROM : Wan, Nathan (CIV)
DATE : Fri Jun 27 22:32:33 2008

Hi all

I'm new to Objective-C and Cocoa and I am having trouble with the notifications system.  This I thought was just a small project to write a native mac program to continuously read and write data from a serial port to a file.  It was suggested I use NSFileHandle to maintain safe threads, as it can read the serial port asynchronously; I had hoped this program would read the text file, and as I changed it, there would be an output to the console.  Something simple to see the notification system in action:

//CODE

#import <Cocoa/Cocoa.h>
#import <Foundation/NSFileHandle.h>
#import <Foundation/NSString.h>
#import <Foundation/NSNotificationCenter.h>
#import <stdio.h>

@interface test : NSObject

-(void) writeDataReadInBackground:(NSNotification *)notification;
-(void) testWriteData:(NSData *)data;

@end

int main(int argc, char *argv[])
{

    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
    NSData *aData = [@"Test" dataUsingEncoding: NSASCIIStringEncoding];
    NSFileHandle *in = [NSFileHandle fileHandleForReadingAtPath:@"/Users/_me_/test.txt"];
 
    if(in == nil)
        printf("somethig wrong\n");
 
    test *t = [[test alloc] init];
 
    [[NSNotificationCenter defaultCenter] addObserver: t selector:@selector(writeDataReadInBackground:) name: NSFileHandleDataAvailableNotification object: nil];

    [t testWriteData: aData];
    [in waitForDataInBackgroundAndNotify];
 
    while(1)
        sleep(5);
 
    [t release];
    [pool release];
 
    return 0;
}

@implementation test
- (void) writeDataReadInBackground:(NSNotification *)notification {
 
    printf("Notification recieved\n");
    }
 
- (void) testWriteData:(NSData *)data {

        NSFileHandle *stdOut = [NSFileHandle fileHandleWithStandardOutput];
     
        [stdOut writeData:data];
     
    }
@end

//END_CODE

Thanks for your help

Nathan

PS  What's the proper way to work between NSString and NSData?