如何在新版本中迁移 NSUserDefaults？
我有一个 iPhone 应用程序，它使用 NSUserDefault standardUserDefaults 存储一些设置。
当我向应用程序添加新功能时，我需要添加新的默认设置，因此我必须迁移/升级 NSUserDefaults。目前，我只是存储版本号并在应用程序启动时检查它。它很快就变得非常混乱，因为我必须添加大量 if 语句。我不能假设用户只是从以前的版本升级，但可能甚至是之前的几个版本。
我喜欢 CoreData 处理迁移表更改的方式，但我想提供 2.2.1 SDK 兼容性，当然 CoreData 与 NSUserDefaults 不同。
有什么建议或最佳实践吗？
I have an iPhone app that stores some settings using NSUserDefault standardUserDefaults.
When I add new features to the app I need to add new default settings and so I have to migrate/upgrade the NSUserDefaults. For now, I just store the version number and check this when the app is launched. It has quickly become very messy as I have to add lots of if statements. I cannot assume that the user is just upgrading from the previous version but perhaps even a couple of versions before.
I like the way that CoreData seems to handle migrating table changes but I want to provide 2.2.1 SDK compatibility and of course CoreData is not the same thing as NSUserDefaults.
Any suggestions or best practices?
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嗯……我不会以这种方式“升级”用户默认值，而是像往常一样查询 NSUserDefaults，只有在未设置默认值的情况下（在这种情况下 objectForKey 将返回 nil），才使用默认值（可能是写回用户默认以节省下次时间）。由于每次读取“新”默认值（即 1.0 中不存在的默认值）时都必须执行此操作，因此我建议执行此操作的包装类/文件，这样代码仅编写一次每个“新”默认值。
另外，虽然问题/问题不同，这个答案在您的情况下也同样有效案件。
Hmm… I wouldn't "upgrade" the user defaults in this way, but instead query NSUserDefaults as usual, only if the default isn't set (objectForKey will return nil in that case), use a default value (which may then be written back to the user defaults to save time the next time). Since you'll have to do this every time a "new" default (i.e. one that didn't exist in 1.0) is read, I advise doing a wrapper class/file that does this, this way the code is written only once for each "new" default.
Also, while the question/problem is different, this answer works just as well in your case.