An AVAudioPlayer Category for playing an Audio (mainly Audio-Sprite) File at a certain time for a certain duration. This Code is already in use in several iOS 5 Apps (that make use of ARC) published by MadameLeRenoir.

AVAudioPlayer+SpriteCategory.h

// AVAudioPlayer+SpriteCategory.h
// Copyright (C) 2012 Tobias Reiss (MIT License)

#import <AVFoundation/AVFoundation.h>

@interface AVAudioPlayer (SpriteCategory)
- (void) playAt:(NSTimeInterval)aStartTime duration:(NSTimeInterval)aDuration;
- (void) playAt:(NSTimeInterval)aStartTime duration:(NSTimeInterval)aDuration completion:(void (^)(void))completionBlock;
- (void) completionCleanup:(NSTimer*)aTimer;

@end

AVAudioPlayer+SpriteCategory.m

// AVAudioPlayer+SpriteCategory.m
// Copyright (C) 2012 Tobias Reiss (MIT License)

// more infos about "Associated Objects":
// http://stackoverflow.com/questions/2846218/how-do-i-use-objc-setassociatedobject-objc-getassociatedobject-inside-an-object
// http://www.techpaa.com/2012/04/adding-properties-to-categories-and.html

#import "AVAudioPlayer+SpriteCategory.h"
#import <objc/runtime.h>

static void * const kMlrAssociatedStorageKey = (void*)&kMlrAssociatedStorageKey;

@implementation AVAudioPlayer (SpriteCategory)

-(void) playAt:(NSTimeInterval)aStartTime duration:(NSTimeInterval)aDuration {
  [self playAt:aStartTime duration:aDuration completion:nil];
}

-(void) playAt:(NSTimeInterval)aStartTime duration:(NSTimeInterval)aDuration completion:(void (^)(void))completionBlock
{
    [self completionCleanup:nil];
    [self setCurrentTime:aStartTime];
    [self play];
  
    NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:aDuration
                                                      target:self
                                                    selector:@selector(completionCleanup:)
                                                    userInfo:completionBlock
                                                     repeats:NO];
    
    objc_setAssociatedObject(self, &kMlrAssociatedStorageKey, timer, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (void)completionCleanup:(NSTimer*)aTimer {
  
    [self pause];
  
    if (aTimer == nil || ![aTimer userInfo]) {
      return;
    }
  
    void (^block)() = (void (^)())[aTimer userInfo];
    block();

    // invalidate NSTimer
    [(NSTimer*)objc_getAssociatedObject(self, &kMlrAssociatedStorageKey) invalidate];
}

@end