if ([[SDImageCache sharedImageCache] imageFromKey:sort.imageUrl]) {
[cell.photoImageView setImage:[[SDImageCache sharedImageCache] imageFromKey:sort.imageUrl]];
} else {
[cell.photoImageView setImageWithURL:[NSURL URLWithString:sort.imageUrl]];
}
SDWebImage从缓存中获取图片
原文：http://www.cnblogs.com/tian-sun/p/5019985.html
