NSTask Runner with NSPipes for StdIn/StdOut/StdErr

//// header
#import <Foundation/Foundation.h>
@class SCTaskRunner;
@protocol SCTaskRunnerDelegate <NSObject>
@optional
- (void) taskRunner:(SCTaskRunner *) taskRunner didReadData:(NSData *) data;
- (void) taskRunner:(SCTaskRunner *) taskRunner didReadDataFromStdOut:(NSData *) data;
- (void) taskRunner:(SCTaskRunner *) taskRunner didReadDataFromStdErr:(NSData *) data;
- (void) taskRunnerTerminated:(SCTaskRunner *) taskRunner;
@end

@interface SCTaskRunner : NSObject {
    BOOL _terminated;
}
@property (assign) NSObject <SCTaskRunnerDelegate> * delegate;
@property BOOL collectDataUntilTerminated;
@property NSTask * task;
@property NSPipe * standardInput;
@property NSPipe * standardOutput;
@property NSPipe * standardError;
@property NSMutableData * data;
- (id) initWithStandardInput:(NSPipe *) pipe;
@end

////implementation

#import "SCTaskRunner.h"

@implementation SCTaskRunner

- (id) init {
    self = [super init];
    self.task = [[NSTask alloc] init];
    self.data = [NSMutableData data];
    [self setupPipesAndNotifications];
    return self;
}

- (id) initWithStandardInput:(NSPipe *) standardInput {
    self = [self init];
    self.standardInput = standardInput;
    return self;
}

- (void) setupPipesAndNotifications {
    self.standardOutput = [[NSPipe alloc] init];
    self.standardError = [[NSPipe alloc] init];
    self.task.standardOutput = self.standardOutput;
    self.task.standardError = self.standardError;

    NSNotificationCenter * nfc = [NSNotificationCenter defaultCenter];

    //add notification to task for termination
    [nfc addObserver:self selector:@selector(taskTerminated:) name:NSTaskDidTerminateNotification object:self.task];

    //add notifications for read data on standard out and standard error
    [nfc addObserver:self selector:@selector(dataAvailable:) name:NSFileHandleDataAvailableNotification object:self.standardOutput.fileHandleForReading];
    [nfc addObserver:self selector:@selector(dataAvailable:) name:NSFileHandleDataAvailableNotification object:self.standardError.fileHandleForReading];
    [self.standardOutput.fileHandleForReading waitForDataInBackgroundAndNotify];
    [self.standardError.fileHandleForReading waitForDataInBackgroundAndNotify];

    if(self.standardInput) {
        self.task.standardInput = self.standardInput;
    }
}

- (void) dataAvailableForFileHandle:(NSFileHandle *) fileHandle {
    NSData * data = [fileHandle availableData];

    if(data.length > 0) {
        if(self.collectDataUntilTerminated) {
            [self.data appendData:data];
        } else {

            if(self.delegate && [self.delegate respondsToSelector:@selector(taskRunner:didReadData:)]) {
                [self.delegate taskRunner:self didReadData:data];
            }

            if(fileHandle == self.standardOutput.fileHandleForReading) {
                if(self.delegate && [self.delegate respondsToSelector:@selector(taskRunner:didReadDataFromStdOut:)]) {
                    [self.delegate taskRunner:self didReadDataFromStdOut:data];
                }
            }

            if(fileHandle == self.standardError.fileHandleForReading) {
                if(self.delegate && [self.delegate respondsToSelector:@selector(taskRunner:didReadDataFromStdErr:)]) {
                    [self.delegate taskRunner:self didReadDataFromStdErr:data];
                }
            }
        }
    }

    if(!_terminated) {
        [fileHandle waitForDataInBackgroundAndNotify];
    }
}

- (void) dataAvailable:(NSNotification *) notification {
    NSFileHandle * fileHandle = notification.object;
    [self dataAvailableForFileHandle:fileHandle];
}

- (void) taskTerminated:(NSNotification *) notification {
    _terminated = TRUE;
    [self dataAvailableForFileHandle:self.standardOutput.fileHandleForReading];
    [self dataAvailableForFileHandle:self.standardError.fileHandleForReading];
    if(self.delegate && [self.delegate respondsToSelector:@selector(taskRunnerTerminated:)]) {
        [self.delegate taskRunnerTerminated:self];
    }
}

- (void) dealloc {
    NSLog(@"DEALLOC: SCTaskRunner");
    [[NSNotificationCenter defaultCenter] removeObserver:self];
    [self.task terminate];
    self.task = nil;
    self.delegate = nil;
    self.standardOutput = nil;
    self.standardError = nil;
    self.standardInput = nil;
}

@end