在iOS应用程序中存储静态数据的最佳方法是什么？

Question

I have in my app a considerable amount of data that it needs to access, but will never be changed by the app. Currently I'm using this data in other applications in JSON files and SQL databases, but neither seems very straightforward to use in iOS.

I don't want to use CoreData, which provides tons of unnecessary functionality and complexity.

Would it be a good idea store the data in PropertyList file and build an accessor class? Are there any simple ways to incorporate SQLite without going the CoreData route?

Answer 1

You can only use plist if the amount of data is relatively small. Plist are entirely loaded into memory so you can only really use them if you can sustain all the objects created by the plist in memory at once for as long as you need them.

Core Data has a learning curve but in use it is usually less complex than SQL. In most cases the "simpler" SQL leads to more coding because you end up having to duplicate much of the functionality of Core Data to shoehorn the procedural SQL into the object-oriented API. You have to manually manage the memory use of all the data by tracking retention. You've write a lot of SQL code every time you want data. I've updated several apps from SQL to Core Data and in all cases the Core Data implementation was smaller and cleaner than the SQL.

Neither is the memory or processor "overhead" any larger. Core Data is highly optimized. In most cases, off the shelf Core Data is more efficient than hand tuned SQL. One minor sub optimization in SQL usually destroys any theoretical advantage it might have.

Of course, if you're already highly skilled at managing SQL in C then you personally might get the app to market more quickly by using SQL. However, if you're wondering what you should plan to use in general on on Apple Platforms, Core Data is almost always the answer and you should take the time to learn it.

Answer 2

You can just use SQLite directly without the overhead of Core Data using the SQLite C API .

Here is a tutorial I found on your use-case - simply loading some data from an SQLite database. Hope this helps.

Answer 3

Depending on the type of your data, the size and how often it changes, you may desire to just keep things simple and use a property list. Otherwise, using SQLite (documented in Jergason's answer) would be where I'd go. Though let me say that if you have a relatively small (less than a couple hundred) set of basic types (arrays, dictionaries, numbers, strings) that don't change frequently, then a property list will be a better choice in my opinion.

As an example to that, in one of my games, I create the levels from a single property list per difficulty. Since there are only a handful of levels per difficulty (99) and a small set of parameters for each (number of elements in play, their initial positions, mass, etc) then it makes sense, and I avoid having to deal with SQLite directly or worse yet, setting up and maintaining CoreData.

Answer 4

What do you mean by "best"? What kind of data?

If it's a bunch of objects, then JSON or (binary) plist aren't terrible formats, since you'll want the whole thing loaded in memory to walk the object graph. Compare space efficiency and loading performance to pick which one to use.

If it's a bunch of binary blobs, then store the blobs in a big file, memory-map the file (NSDataReadingMapped aka NSMappedRead), and use indexes into the blobs. iOS frameworks use a mixture of these (eg there are a lot of .pngs, but also "other.artwork" which just contains raw image data).

You can also use NSKeyedArchiver and friends if your classes implement the NSCoding protocol, but there's some object graph management overhead and the plist format it produces isn't exactly nice to work with.