// ViewController.h
@interface ViewController : UIViewController {

    IBOutlet UISlider *aSlider;
    IBOutlet UISlider *anotherSlider;

}

@property (retain, nonatomic) IBOutlet UISlider *aSlider;
@property (retain, nonatomic) IBOutlet UISlider *anotherSlider;

// ViewController.m
@interface ViewController ()

@end

@implementation ViewController
@synthesize aSlider;
@synthesize anotherSlider;

-(void)resetSliders
{
    NSLog(@"Resetting sliders sl1: %@ sl2: %@", aSlider, anotherSlider);
    [aSlider       setTo:0.5f animated:NO];
    [anotherSlider setTo:0.5f animated:NO];
}

- (IBAction)setOneSlider:(UISlider *)sender {
    NSLog(@"Setting aSlider to %f", sender.value);
    self.sl1Val = sender.value;
    [self doAThing];
}

- (IBAction)setTwoSlider:(UISlider *)sender {
    NSLog(@"Setting anotherSlider to %f", sender.value);
    self.sl2Val = sender.value;
    [self doBThing];
}

2015-04-28 12:22:19.608 GenShock[4489:681127] Resetting sliders sl1: (null) sl2: (null)

@property (retain, nonatomic) IBOutlet UISlider *aSlider;
@property (retain, nonatomic) IBOutlet UISlider *anotherSlider;