AVAudioPlayer isPlaying crashing app - objective-c

Question

I'm using an AVAudioPlayer to manage some sounds but the isPlaying method seems to be crashing.
done when I initiate the page:
self.soundClass = [AVAudioPlayer alloc];
how I play the sound:
-(void)playSound:(NSString *)fileName:(NSString *)fileExt {
if ( [self.soundClass isPlaying] ){
[self.soundClass pause];
}
else if (newSoundFile == currentSoundFile) {
[self.soundClass play];
}
else {
NSLog(#"PlaySound with two variable passed function");
[[NSBundle mainBundle] pathForResource: fileName ofType:fileExt]], &systemSoundID);
[self.soundClass initWithContentsOfURL:[NSURL fileURLWithPath: [[NSBundle mainBundle] pathForResource: fileName ofType:fileExt]] error:nil];
[self.soundClass prepareToPlay];
[self.soundClass play];
}
self.currentSoundFile = fileName;
}
My soundClass is pretty empty right now:
soundclass.h
#import <UIKit/UIKit.h>
#import <AudioToolbox/AudioToolbox.h>
#import<AVFoundation/AVFoundation.h>
#interface SoundClass : AVAudioPlayer <AVAudioPlayerDelegate> {
}
#end
SoundClass.m
#import "SoundClass.h"
#implementation SoundClass
-(void)dealloc {
[super dealloc];
}
#end
Do you see anything here I might be doing wrong? It crashes right at if ( isPlaying )

Answer 1

You point to space that is allocated for an instance of AVAudioPlayer in the first line you list, but you don't actually initialize an instance. In Cocoa, "alloc" is 99.9% of the time followed by some form of -init (like -initWithContentsOfURL:error: in the case of AVAudioPlayer).
Also, "soundClass" is an odd name for an instance variable. You should read up on the difference between a class (the blueprint of an object) and an instance of a class (an actual object built from the blueprint). Solid knowledge of this concept is critical to your understanding of Cocoa (and all object-oriented) programming.