iOS：如何保存在应用程序中创建的自定义对象
我一直在阅读有关保存对象、保留状态等的内容，但我仍然对保存从我的应用程序创建的对象时应该采取的路线感到有点困惑。我构建了一个应用程序，用户可以在其中创建带有流派、名称和频率的广播电台。一旦用户点击保存，就会使用自定义类创建一个“RadioStation”对象，并将其存储在放置在 RootViewController 中的 NSMutableArray 中。虽然 RadioStation 对象可以存储在该数组中并在表视图中正确显示，但很明显，一旦应用程序退出，这些对象将不再由应用程序保留。
此时我不确定应该如何开始构建这个设计。我需要设置一个 plist 吗？我应该将 Core Data 与 SQLite DB 一起使用吗？我是否需要针对这两种情况研究 iOS 对象序列化？还是有我不知道的更直接的方法？
I've been reading up on saving objects, preserving state etc, but I'm still a little confused on the route I should take when saving objects that are created from my app. I have built an app where a user can create a Radio Station with the Genre, name and frequency. Once a user hits save, a "RadioStation" object is created using a custom class and is stored in an NSMutableArray that is placed in the RootViewController. While RadioStation objects can be stored in this array and are displayed correctly in the table view, it's obvious that once the application quits, these are no longer going to be held by the application.
At this point I'm not sure how I should begin to architect this design. Do I need to set up a plist? Should I use Core Data with a SQLite DB? Do I need to research iOS object serialization for both these scenarios? Or is there an more straight forward way that I'm not aware of?
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有三种方法可以在本地保存数据：
如何保存对象数据取决于您的使用方式它以及您要保存的数据类型。如果您有很多相同类型的对象，并且 SQL 的搜索和排序机制会很有用，那么 CoreData 就有意义。我倾向于将沙箱用于非常大的文件，例如图像、声音文件和通过 NSData 反弹的大量数据。我将 UserDefaults 用于可能被视为“首选项”的少量数据。
您可以将任何内容放在您想要的任何位置，我建议您在开始新项目时熟悉所有三种机制。其他技术（例如使用 NSCoding 来序列化和反序列化类）可用于更轻松地保存数据。请注意，一旦实现了 NSCoding，您就可以将数据存储在任何地方，甚至可以通过网络发送数据。
对于您的 RadioStation，我个人会使用 UserDefaults。使用 NSCoding 的好处是，一旦实现了 initWithCoder 和encodeWithCoder，您就可以相当轻松地流式传输对象的层次结构（例如自定义对象的数组，每个对象可能包含字典、数组或自定义对象等）。如果您唯一保存的是字符串数组，那么直接使用 UserDefaults 就足够简单了。
There are three ways to persist data locally:
How you persist your object data depends on how you're using it, and what type of data you're saving. CoreData makes sense if you have a lot of objects of the same type and SQL's search and sorting mechanisms would be useful. I tend to use the sandbox for very large files, eg images, sound files, and large agglomerations of data bounced through NSData. And I use UserDefaults for small amounts of data that might be considered "preferences".
You can put anything anywhere you want, and I suggest being familiar with all three mechanisms when you start a new project. Additional techniques, like using NSCoding to serialize and deserialize classes, can be used to make saving data easier. Note that once you've implemented NSCoding, you could store data anywhere and even send it over the wire.
For your RadioStation, I would personally use UserDefaults. The benefit of using NSCoding is that, once you implement initWithCoder and encodeWithCoder, you can stream a hierarchy of objects (eg an array of custom objects, each of which might contain a dictionary, array, or custom object, etc) fairly easily. If the only thing you're saving is an array of strings, then directly using UserDefaults is easy enough.
最强大的方法是使您的自定义对象成为
NSManagedObject的子类，并使用 Core Data 将其存储在NSManagedObjectContext中。在 iOS 上，这将始终使用 sqlite 数据库，在 Mac OS X 上，您可以使用 sqlite、xml 或专有的二进制格式（比 xml 更小/更快）。根据您的数据结构的复杂程度以及未来更改的可能性，此技术对于您的应用程序来说可能太复杂，也可能不太复杂。设置工作量很大，API 也非常复杂，但如果您需要在文件中存储数万/数百万个对象，那么它是最佳选择。
对于您的应用程序，我将有一个包含应用程序中所有广播电台的 sqlite 文件。
最简单的选择是在自定义对象的类中实现 NSCoding 协议。此处记录：
http://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/Archiving/Articles/codingobjects.html#//apple_ref/doc/uid/20000948-BCIHBJDE
基本理论是您的对象将其所有数据写入或读取到“编码器”，然后将编码器传递给任何子对象。在类之外，您可以使用“归档器”或“解归档器”类来协调一切。
一旦您的自定义类实现了 NSCoding，您就可以使用以下方法将其读/写到磁盘：
这是一种非常简单的方法，但它有一些缺点，例如您需要找出自己的方法支持不同版本的文件格式（例如可能具有不同的文件扩展名）。
Cocoa/CocoaTouch 中的许多类已经实现了
NSCoding，因此可以通过这种方式将它们写入文件（包括NSArray、NSString、>NSNumber等）。对于您的应用程序，我将使用它将每个广播电台存储在单个文件中。当应用程序启动时，从目录加载所有广播电台。您应该考虑为您的应用启用 iTunes 拖放文件共享，以便用户可以轻松地与朋友或在设备之间共享广播电台文件。
这也非常适合 iCloud 在设备之间进行同步，我没有深入研究 iCloud，但我预计每个广播电台一个文件将是实现 iCloud 同步的理想方式。
The most powerful approach is to make your custom object a subclass of
NSManagedObject, and store it in anNSManagedObjectContextusing Core Data. On iOS this will always use an sqlite database, on Mac OS X you can use sqlite, xml, or a proprietary binary format (smaller/faster than xml).Depending on how complicated your data structure is, and how likely it is to change in future, this technique may or may not be too complicated for your app. It's a lot of work to setup, and the API is very complicated, but it's the best choice if you need to store tens of thousands/millions of objects in a file.
For your app, I would have a single sqlite file containing all of the radio stations in the app.
The simplest option, is to implement the
NSCodingprotocol in your custom object's class. Documented here:http://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/Archiving/Articles/codingobjects.html#//apple_ref/doc/uid/20000948-BCIHBJDE
The basic theory is your object writes or reads all it's data to a "coder", and then passes the coder on to any child object(s). Outside of the class, you use an "archiver" or an "unarchiver" class to coordinate everything.
Once your custom class implements
NSCodingyou can read/write it to the disk with:This is a very simple approach, but it has a few drawbacks, for example you will need to figure out your own way to support different versions of the file format (perhaps with a different file extension for example).
Many classes in Cocoa/CocoaTouch already implement
NSCoding, so they can be written to a file in this fashion (includingNSArray,NSString,NSNumber, etc).For your app, i would use this to store each radio station in a single file. When the app launches, load all the radio stations from a directory. You should consider enabling iTunes drag/drop filesharing for your app, so users can easily share radio station files with their friends or between devices.
This would also fit in well with iCloud for syncing between devices, I haven't looked into iCloud much, but I expect one file per radio station will be the ideal way to implement iCloud syncing.
不需要这样的东西。如果你只需要保存一件事，那么研究一下 NSArray 的这种方法：
我你的用户可以保存许多广播电台，那么你可能想看看 CoreData，它有一点曲线，但最终将是最简单的方法。
No need for such things. If you only have like one thing to save, then research this method of NSArray:
I your user can save many radio stations, then you might want to look into CoreData, which has a bit of a curve, but ultimately will be the easiest way.