数字＋字符的字符串 修改数字字体方法

    NSString* string = @"60秒";

    NSMutableAttributedString * attStr = [[NSMutableAttributedStringalloc] initWithString:string];

   NSRange range = NSMakeRange (0,2);

    [attStr setAttributes:@{NSFontAttributeName : [UIFontsystemFontOfSize:18.0 *kScreenWidth]}range:range];

    [self.button setAttributedTitle:attStrforState:UIControlStateNormal];