NSUserDefaults的局限性是什么？ [英] What are the limitations of NSUserDefaults?
问题描述
在iPhone中永久存储数据通常使用Core Data或sqlite3来完成。大多数人喜欢使用NSUserDefaults作为应用程序首选项的存储，而不是将其用作普通数据库（如sqlite）。
Storing data permanently in an iPhone is usually done using Core Data or sqlite3. Most people prefer to user NSUserDefaults as a storage for application preferences, rather than using it as a normal database (such as sqlite).
我发现大量数据可以存储在NSUserDefaults，它是非常容易使用，它是快速。那么为什么不使用这个永久存储？
NSUserDefaults作为数据库的限制是什么？
I have found that large amount of data can be stored in NSUserDefaults, it is extremely easy to use and it is fast. So why not use this as a permanent storage? What are the limitations of NSUserDefaults as a database?
更新：
我经常使用三种不同的
Update:
I frequently use three different ways of saving my data to disk.
- 核心数据
- 将对象序列化到plists
- NSUserDefaults
我不再使用FMDB
每种方法的主要优点和缺点是什么？
I do not use FMDB (or sqlite directly) anymore. What are the main advantages and disadvantages of each approach?
我遇到的NSUserDefaults的一些优点：
Some advantages of NSUserDefaults that I've come across:
- 分组等可以很容易地使用NSPredicate来完成。
- NSUserDefaults是线程安全的。
- 它需要一行来获取和保存数据到NSUserDefaults。
推荐答案
NSUserDefaults提供了一个简单的学习曲线和线程安全的实现。
NSUserDefaults offers a trivial learning curve and thread safe implementation.
否则我发现Core Data在各方面都有优势。特别是关于配置默认值和迁移例程。
Otherwise I've found Core Data superior in every way. Especially with regards to configuring default values and migration routines.
编辑：事实证明，NSUserDefaults线程安全性似乎来自主线程上的运行操作。这在我的一个应用程序中造成严重的跳帧;我结束了剥离NSUserDefaults，并将其替换为一个线程安全的NSMutableDictionary，它被序列化到一个文件。
As it turns out, NSUserDefaults "thread-safeness" seems to come from running operations on the main-thread. This caused severe frame-skipping in one of my applications; I ended up ripping out NSUserDefaults and replacing it with a thread-safe NSMutableDictionary which gets serialized to a file.
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