KerningLabel.h

#import <UIKit/UIKit.h>

IB_DESIGNABLE
@interface KerningLabel : UILabel

@property (nonatomic) IBInspectable CGFloat kerning;

@end

KerningLabel.m

#import "KerningLabel.h"

@implementation KerningLabel

- (void)setKerning:(CGFloat)kerning
{
    NSMutableAttributedString *attribString = [[NSMutableAttributedString alloc]initWithAttributedString:self.attributedText];
    [attribString addAttribute:NSKernAttributeName value:@(kerning) range:NSMakeRange(0, self.attributedText.length)];
    self.attributedText = attribString;
}

@end