Just call [self sliderValue:nil];
also if you don't need sender
as a in parameter to your actions you can omit them when developing for iOS.
- (IBAction)sliderValue {
}
Better yet (in my opinion) would be to set the value in viewDidLoad
directly in case you add stuff later to sliderValue method. It's really two different thing one should handle logic for the slider changing value while the odder just sets the default value.
sliderLabel.text = [NSString stringWithFormat:@"%g", roundf(slider.value)];