NSTask subclass problem

oh, you are right, I guessed there were some theoretical reason, and I shifted to has-a

this was my (is-a) code:

@interface dcm2niiTask : NSTask
...
int main (int argc, const char * argv[]) {
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
dcm2niiTask *myTask;

myTask = [[dcm2niiTask alloc] init];
[myTask setLaunchPath: @"/bin/ls"];

NSArray *arguments;
arguments = [NSArray arrayWithObjects: @"-l", @"-a", @"-t", nil];
[myTask setArguments: arguments];

NSPipe *pipe;
pipe = [NSPipe pipe];
[myTask setStandardOutput: pipe];

NSFileHandle *file;
file = [pipe fileHandleForReading];

[myTask launch];

NSData *data;
data = [file readDataToEndOfFile];

NSString *string;
string = [[NSString alloc] initWithData: data encoding: NSUTF8StringEncoding];
NSLog (@"woop! got\n%@", string);

[myTask release];
[pool drain];
return 0;


All was right if I used
myTask = [[NSTask alloc] init];
instead of
myTask = [[dcm2niiTask alloc] init];

thanks,

Fabrizio

a lot of square brackets in the previous code where deleted,

as in [ myTask setLaunchPath: @"/bin/ls" ];

I don't know how to avoid it, sorry

fabrizio

now I'm working with myTask (instance of NSTask) as a member of dcm2niiTask (has-a instead of is-a)

is it reasonable?

fabrizio

thanks for the brackets,

yes I didn't write all the code,

there was the .h file with @interface dcm2niiTask : NSTask
members and methods,

there was the .m file with @implementation etc,

but the problem arises in the main program, basically when my object is declared as NSTask it is all right, when it is declared as dcm2niiTask (subclass of NSTask) in execution it is noticed that the method is abstract and that I have to declare it in my subclass...

fabrizio

I need to create a plugin for a medical image client/server software (Osirix) and I need to execute inside the plugin a shell script (dcm2nii, by Chris Rorden) that implements a conversion of medical format file (DICOM) in a research format one (Nifti).

I though to instruct a class (dcm2niiTask) to perform the conversion and to manage other staff concerning it. The main task of the class is to perform the conversion, i.e. to call the shell script.

that's all

fabrizio

yes, i'm now using an NSTask object in my class (has-a), as I posted previously,

but still I would like to understand why the subclassing process failed... this is because I'm working with objective-C since two days, and it is not clear to me if it is a bug or a my misunderstanding of inheritance applied to foundation classes.

fabrizio

HI,

This is my code, in three files (last one containing main)

//
// FF_dcm2niiTask.h
// FF_dcm2nii
//
// Created by Fabrizio Fasano on 1/13/10.
// Copyright 2010 _MyCompanyName_. All rights reserved.
//
#import <Cocoa/Cocoa.h>
@interface FF_dcm2niiTask : NSTask
{
 int aNumber;
}
-(void) chooseSource;
-(void) executeTask;
-(void) printaNumber;
@end
//
// FF_dcm2niiTask.m
// FF_dcm2nii
//
// Created by Fabrizio Fasano on 1/13/10.
// Copyright 2010 _MyCompanyName_. All rights reserved.
//
#import "FF_dcm2niiTask.h"
@implementation FF_dcm2niiTask
-(void) chooseSource
{
 aNumber=1;
}
-(void) executeTask
{
 aNumber=2;
}
-(void) printaNumber
{
 NSLog(@"the aNumber value is: %i", aNumber);
}
@end
#import <Foundation/Foundation.h>
#import "FF_dcm2niiTask.h"
int main (int argc, const char * argv[]) {
 NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
 FF_dcm2niiTask *myTask;
 myTask = [FF_dcm2niiTask alloc];
 [myTask init];
 [myTask setLaunchPath: @"/bin/ls"];
 
 NSArray *arguments;
 arguments = [NSArray arrayWithObjects: @"-l", @"-a", @"-t", nil];
 [myTask setArguments: arguments];
 
 NSPipe *pipe;
 pipe = [NSPipe pipe];
 [myTask setStandardOutput: pipe];
 
 NSFileHandle *file;
 file = [pipe fileHandleForReading];
 
 [myTask launch];
 
 NSData *data;
 data = [file readDataToEndOfFile];
 
 NSString *string;
 string = [[NSString alloc] initWithData: data encoding: NSUTF8StringEncoding];
 NSLog (@"woop! got %@", string);
 
 // work with class
 [myTask chooseSource];
 [myTask printaNumber]; 
 [myTask executeTask];
 [myTask printaNumber];
 
 [myTask release];
 [pool drain];
 return 0;
}

oh, it seems you addressed the problem,

I have to learn something more on these issues (clusters etc)

anyway concerning the practical problem it seems composition is to be preferred,

thanks again,

fabrzio