GCD异步加载网络图片

    dispatch_queue_t network_queue;
    network_queue = dispatch_queue_create("com.myapp.network", nil);
    
    dispatch_async(network_queue, ^{
        UIImage *cellImage = [self loadMyImageFromNetwork:[self.content objectAtIndex:indexPath.row]];
        
        // 回到主线程
        
        dispatch_async(dispatch_get_main_queue(), ^{
            
            // 显示图片到界面
            cell.imageView.image = cellImage;
            [cell setNeedsLayout];
            
        });
    } );

另附：

使用UIImageView展现来自网络的图片

关键字：异步加载、图片缓存

http://blog.csdn.net/jasonblog/article/details/7352483