iOS的UILable一行显示多样字符

要现实AABBBBB的效果：

 

        NSString *aString = @"AABBBBB";
        NSMutableAttributedString *attriString = [[NSMutableAttributedString alloc]
                                                  initWithString:aString];
        //把AA的字体颜色变为红色
        [attriString addAttributes:@{NSForegroundColorAttributeName:
                                         [UIColor redColor],
                                     NSFontAttributeName:
                                         [UIFont boldSystemFontOfSize:14]}
                             range:NSMakeRange(0, 2)];
        
        [attriString addAttributes:@{NSForegroundColorAttributeName:
                                         [UIColor blackColor],
                                     NSFontAttributeName:
                                         [UIFont boldSystemFontOfSize:18]}
                             range:NSMakeRange(2, aString.length - 2)];
        
        //显示文本
        [aLable setAttributedText:attriString];