Preferred way of storing data in OS X/Cocoa? [duplicate] - objective-c

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Closed 11 years ago.
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iOS store just a little bit of data
New OS X dev here. I have a modicum of user data I need to store (just paths to recently opened files, really). What is the preferred way of storing these in Cocoa land? I've heard of Core Data before but, as a Windows dev who has encountered tons of APIs from MS like this, does anyone actually use this?
I could just write everything to my own file, of course, but I'd prefer to do things The Right Way(TM).
Any suggestions would be great!

Answer 1

If your application is document based, the list of recently opened files is automatically stored for you. If you need to store them yourself, then I would suggest using NSUserDefaults. It is the most common way to store lightweight information such as preferences and recently used items.
Yes, people do use core data, but it is usually used for more complex data, such as a document with different parts.

Answer 2

See my answer to this thread for five suggestions for storing data. Although that thread covers iOS and therefore Cocoa Touch instead of Cocoa, the answers are all pretty much the same.
Note that the first answer, NSUserDefaults, is meant for saving data like app preferences. That might be most appropriate if the application will always want to load the same set of data; if the data is more like a document, where you might have different sets of data stored in different files, you should use one of the other methods. Writing a property list would probably be simplest in this case:
// store some words in an array and write to a file at pathToFile
NSMutableArray *array = [NSMutableArray array];
[array addObjects: #"foo", #"bar", #"baz", nil];
[array writeToFile:pathToFile];
// (later) read contents of the file at pathToFile into a new array
NSArray *words = [NSArray arrayWithContentsOfFile:pathToFile];
As for Core Data, yes, many people use it. It's a very nice way to manage persistent objects. However, it sounds like it's way more than you need for just storing a bunch of paths.

Answer 3

As ughoavgfhw mentioned, the NSDocument architecture already takes care of keeping a list of recent documents. (If you look through your Preferences folder, the *.LSSharedFileList.plist preference files hold this data).
If you take a look at those files in Property List Editor or Xcode 4, you'll see the preferred way to store a reference to a file in a persistent manner is to use Alias (or "Bookmark") data. If you're coming from a Windows/*nix background, alias data can keep track of an item even if it's renamed or moved.
If you need to store a list of recent files by yourself, and can require OS X 10.6+, you can use NSUserDefaults, along with the bookmark data functionality found in NSURL.
In your method that opens files, you could do something like this:
NSString * const MDRecentDocumentsKey = #"MDRecentDocuments";
- (void)application:(NSApplication *)sender openFiles:(NSArray *)filenames {
// assume single item
NSURL *URL = [NSURL fileURLWithPath:[filenames objectAtIndex:0]];
NSMutableArray *recentAppBookmarks =
[[[[NSUserDefaults standardUserDefaults] objectForKey:MDRecentDocumentsKey]
mutableCopy] autorelease];
// assume 20 item limit
if ([recentAppBookmarks count] + 1 > 20) {
[recentAppBookmarks removeLastObject];
}
NSData *data = [ bookmarkDataWithOptions:0 includingResourceValuesForKeys:nil
relativeToURL:nil error:NULL];
[recentAppBookmarks insertObject:data atIndex:0];
[[NSUserDefaults standardUserDefaults] setObject:recentAppBookmarks
forKey:MDRecentDocumentsKey];
}
To get the list of recent files at app launch, you could do something like this:
- (void)awakeFromNib {
recentAppURLs = [[NSMutableArray alloc] init];
NSArray *recentAppBookmarks =
[[NSUserDefaults standardUserDefaults] objectForKey:MDRecentDocumentsKey];
for (NSData *bookmarkData in recentAppBookmarks) {
NSURL *resolvedURL = [NSURL URLByResolvingBookmarkData:bookmarkData
options:NSURLBookmarkResolutionWithoutUI|NSURLBookmarkResolutionWithoutMounting
relativeToURL:nil bookmarkDataIsStale:NULL error:NULL];
if (resolvedURL) [recentAppURLs addObject:resolvedURL];
}
}
Otherwise, if you need compatibility with OS X 10.5 and earlier, I posted some categories on NSString in this answer.