UILabel+ktlib.h

#import <Foundation/Foundation.h>

@interface UILabel (ktlib)

- (void) fitSizeOfFont:(UIFont *)font;

@end

UILabel+ktlib.m

#import "UILabel+ktlib.h"

@implementation UILabel (ktlib)

- (void) fitSizeOfFont:(UIFont *)font {
   NSString *label = self.text;

   CGFloat width  = self.frame.size.width;
   CGFloat height = self.frame.size.height;
   CGSize constraintSize = CGSizeMake(width, MAXFLOAT);
   CGSize labelSize;

   int i;
   for(i = font.pointSize; i > self.minimumFontSize; i--) {
      font = [font fontWithSize:i];

      labelSize = [label sizeWithFont:font constrainedToSize:constraintSize lineBreakMode:UILineBreakModeWordWrap];

      if(labelSize.height <= height)
         break;
   }

   self.font = font;
}

@end