error: 'fxVolumeSlider' undeclared (first use in this function) - Need to declare IBOUTLET?

Okay well now im trying to get the volume to change on the slider

here is the code

@implementation MainerViewController
@synthesize fxVolumeSlider;

- (IBAction)pushPlay:(id)sender; {
    NSString *path = [[NSBundle mainBundle] pathForResource:@"test" ofType:@"wav"];
    if (theAudio) [theAudio release];
    theAudio = [[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL fileURLWithPath:path] error:NULL];
    theAudio.delegate = self;
    [theAudio play];    
    volumeTimer = [NSTimer scheduledTimerWithTimeInterval:0.05 target:self selector:@selector(updateVolume) userInfo:nil repeats:YES];

}

-(void)updateVolume {
    [theAudio setVolume:fxVolumeSlider.value];
}

- (void)viewDidLoad {
    [super viewDidLoad];

    // Setup custom slider images
    UIImage *minImage = [UIImage imageNamed:@"grey_track.png"];
    UIImage *maxImage = [UIImage imageNamed:@"white_track.png"];
    UIImage *tumbImage= [UIImage imageNamed:@"metal_screw.png"];

    minImage=[minImage stretchableImageWithLeftCapWidth:10.0 topCapHeight:0.0];
    maxImage=[maxImage stretchableImageWithLeftCapWidth:10.0 topCapHeight:0.0];

    // Setup the FX slider
    [fxVolumeSlider setMinimumTrackImage:minImage forState:UIControlStateNormal];
    [fxVolumeSlider setMaximumTrackImage:maxImage forState:UIControlStateNormal];
    [fxVolumeSlider setThumbImage:tumbImage forState:UIControlStateNormal];

    fxVolumeSlider.minimumValue = 0.0;
    fxVolumeSlider.maximumValue = 1.0;
    fxVolumeSlider.continuous = YES;
    //fxVolumeSlider.value = [sharedSoundManager fxVolume];

    // Attach an action to sliding
    [fxVolumeSlider addTarget:self action:@selector(fxSliderAction:) forControlEvents:UIControlEventValueChanged];

    // Cle开发者_如何学JAVAanup
    minImage = nil;
    maxImage = nil;
    tumbImage = nil;
}
- (void) fxSliderAction:(id)sender {
    [theAudio setFxVolume:fxVolumeSlider.value];
}

However i now get this error

warning: 'AVAudioPlayer' may not respond to '-setFxVolume:'

So everytime i play the play button, i try to adjust the volume but i get kicked out of the app

You've declared both the ivar and the property as _fxVolumeSlider but what you use within the method is fxVolumedSlider. Both are not the same. You should use _fxVolumeSlider or what you probably meant was to declare the property as

@property(retain, nonatomic) IBOutlet UISlider *fxVolumeSlider;

and synthesize it using

@synthesize fxVolumeSlider = _fxVolumeSlider;

But even then you can't use it as fxVolumeSlider. You can use it as self.fxVolumeSlider or _fxVolumeSlider. If you want to use it as plain fxVolumeSlider, you should replace all _fxVolumeSliders with fxVolumeSlider.

Check the underscore in the declaration. In the .h file, you have:

IBOutlet UISlider *_fxVolumeSlider;

You should have:

IBOutlet UISlider *fxVolumeSlider;

Also, in the .m file, edit the line

@synthesize _fxVolumeSlider;

to be

@synthesize fxVolumeSlider;

As to your revised issue:

- (void) fxSliderAction:(id)sender {
    [theAudio setFxVolume:fxVolumeSlider.value];
}

should instead read as

- (void) fxSliderAction:(id)sender {
    [theAudio setVolume:fxVolumeSlider.value];
}

Watch out for typos (and look for them before posting!)