使用场景：
一个UILabel+UIImageView来实现，label动态宽度，你再去设置imageView的frame？折行呢？刚好到边界呢？就很蛋疼

  UILabel *lab = [[UILabel alloc]initWithFrame:CGRectMake(20, 120, self.view.frame.size.width-40, 20)];
    lab.backgroundColor = [UIColor orangeColor];
    NSMutableAttributedString *attStr = [[NSMutableAttributedString alloc]initWithString:@"拉轰的小哥"];
    //要插入的图片
    NSTextAttachment *attach = [[NSTextAttachment alloc] init];
    UIImage *img = [UIImage imageNamed:@"demand"];
    attach.image = img;
    //获取图片大小
    CGFloat imgH = img.size.height;
    CGFloat imgW = img.size.width;
   
    //依靠Label的descender下基准计算图片的偏移量
    CGFloat textPaddingTop = lab.font.descender+(lab.font.pointSize-imgH)*0.5;
    
    attach.bounds = CGRectMake(0, textPaddingTop , imgW, imgH);
    NSAttributedString *imgStr = [NSAttributedString attributedStringWithAttachment:attach];

    [attStr appendAttributedString:imgStr];
    lab.attributedText = attStr;
    
    [self.view addSubview:lab];
    

展示实现效果：