字体大小自适应

label.adjustsFontSizeToFitWidth = YES;

- (void)setFontSizeThatFits:(UILabel*)label
{
 
    CGFloat fontSizeThatFits;
    
    [label.text sizeWithFont:label.font
                 minFontSize:12.0   //最小字体
              actualFontSize:&fontSizeThatFits
                    forWidth:label.bounds.size.width
               lineBreakMode:NSLineBreakByWordWrapping];
    
    label.font = [label.font fontWithSize:fontSizeThatFits];
  
}