//动态设置cell的高度
+ (CGFloat)heightForRowWithModel:(PhotoInfo *)photoInfo
{
    //1.图片的高度
    //让图片等比例缩放
    //(1)获取图片
    UIImage *image = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"ZZ" ofType:@"png"]];
    CGFloat imageHeight = [self heightForImage:image];
    //2.文本的高度
    CGFloat textHeight = [self heightForText:photoInfo.introduction];
    //3.返回cell 的总高度
    return kPhotoCell_TitleLabel_Height + imageHeight + textHeight + 4 * kPhotoCell_MarginBetween;
}
//单独计算图片的高度
+ (CGFloat)heightForImage:(UIImage *)image
{
    //(2)获取图片的大小
    CGSize size = image.size;
    //(3)求出缩放比例
    CGFloat scale = kPhotoCell_Width / size.width;
    CGFloat imageHeight = size.height * scale;
    return imageHeight;
}
//单独计算文本的高度
+ (CGFloat)heightForText:(NSString *)text
{
    //设置计算文本时字体的大小,以什么标准来计算
    NSDictionary *attrbute = @{NSFontAttributeName:[UIFont systemFontOfSize:kFontSize]};
    return [text boundingRectWithSize:CGSizeMake(kPhotoCell_Width, 1000) options:NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading attributes:attrbute context:nil].size.height;
}