NSFetchedResultController 问题
我目前正在使用 NSFetchedResultController 来获取显示的数据。 不过我有两个问题：
1）当我将 fetchSizeBatch 属性设置为 2 时，我的应用程序总是崩溃。 fetchSizeBatch 的实际含义是什么？我真的不想将其设置为 2，我只是在玩它并注意到了该错误。
2) 我的应用程序当前在滚动 UITableView 时使用大约 25 MB 的内存。我认为 NSFetchedResultController 是造成这种情况的原因。 25MB还正常吗？或者这个控制器是某种指定的设备？
I'm currently using NSFetchedResultController to get the to displayed data.
However I've got two question about it:
1) When I set the fetchSizeBatch property to 2, my app always crashes.
What does fetchSizeBatch actually mean? I don't really want to set it to 2, I was just playing with it and noticed that bug.
2) My app currently uses about 25 MB of memory while scrolling through the UITableView. I assume NSFetchedResultController is causing that. Is 25 MB still normal? Or is this controller some sort of device specified?
如果你对这篇内容有疑问，欢迎到本站社区发帖提问 参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。
绑定邮箱获取回复消息
由于您还没有绑定你的真实邮箱，如果其他用户或者作者回复了您的评论，将不能在第一时间通知您！
发布评论
评论（1）
对于核心数据批量大小而言，2 是一个极低的数字。 根据文档，它可能比我解释得更好，设置批量大小意味着数据将在批次；换句话说，Core Data 查询数据库以获取排序结果，但仅将批量大小指定的数量拉入托管对象。这个的实现 - 这是最重要的部分 - 是 NSArray 的代理子类，每当访问每个批次的项目时，无论是通过索引、枚举还是其他方式，它将分页。在您的例子中，这意味着 Core Data 每两个对象就会往返一次数据库。对于与 UITableView 通信的 NSFetchedResultsController，您可以看到这是一个多么严重的问题。
否则，25MB 并不理想，但我见过应用程序的表现更糟糕。我想说你很好。
Two is an extremely low number for a Core Data batch size. According to the documentation, which probably explains it much better than I do, setting a batch size means that the data will be processed in batches; in other words, Core Data queries the database for the sorted results but only pulls the amount specified by the batch size into managed objects. The implementation of this - and this is the big part - is a proxy subclass of NSArray which will page in items from each batch whenever they're accessed, either by index, enumeration, whatever. In your case, this means that Core Data is taking a round trip back to the database every two objects. For an NSFetchedResultsController talking to a UITableView, you can see how much of a problem this is.
Otherwise, 25MB isn't fantastic, but I've seen apps do much worse. I would say you're good.