What is the best way to store an array of objects with cocoa?

Question

I have an NSMutableArray with many objects in it. Some are NSStrings, others are NSMutableArrays, others are NSNumbers. What is the best way to store this data so that the app could use it again?

The array needs to stay in order as well.

I'm thinking a plist or NSUserDefaults?

Many thanks

Anne · Accepted Answer · 2011-05-31 20:47:14Z

3

Consider using NSKeyedArchiver.

// Archive
NSData *data = [NSKeyedArchiver archivedDataWithRootObject:theArray];
NSString *path = @"/Users/Anne/Desktop/archive.dat";
[data writeToFile:path options:NSDataWritingAtomic error:nil];

// Unarchive
NSString *path = @"/Users/Anne/Desktop/archive.dat";
NSMutableArray *theArray = [NSKeyedUnarchiver unarchiveObjectWithFile:path];

It works great, especially in case the array contains more then strings and numbers.
This way you can be sure the unarchived array is identical to the original.

edited May 31, 2011 at 20:47

answered May 31, 2011 at 20:34

Anne

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alexhajdu · Accepted Answer · 2013-02-06 22:38:36Z

2

Assuming the other arrays also contain only numbers, strings, and arrays (or other property list types), a plist would be a great way to store your data. It will keep it's order, and is simple to use.

To write an array to a plist file, use writeToFile:atomically:.

[myArray writeToFile:@"path/to/file.plist" atomically:YES];

To read it, use initWithContentsOfFile:.

myArray = [[NSMutableArray alloc] initWithContentsOfFile:@"path/to/file.plist"];

However, that will create a mutable array with non-mutable contents. To create an array with mutable contents, you can use CFPropertyListCreateDeepCopy.

NSArray *temp = [[NSArray alloc] initWithContentsOfFile:@"path/to/file.plist"];
myArray = (NSMutableArray*) CFPropertyListCreateDeepCopy(kCFAllocatorDefault,(CFArrayRef)temp,kCFPropertyListMutableContainers);
[temp release];

edited Feb 6, 2013 at 22:38

alexhajdu

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answered May 31, 2011 at 20:01

ughoavgfhw

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1 Comment

Joshua Nozzi Over a year ago

The "only contains numbers strings and arrays" (and dates and dictionaries and NSData and NSNull) part, along with the "creates an immutable array" part are only true if you're using NSUserDefaults or writing out to a PLIST. PLIST (and user defaults, same format) only allows those types BUT if your class can be archived/unarchived, it can be stored as an NSData instance inside a PLIST/user defaults just fine. If you're going with keyed archiving, as Anne suggested above, you might as well store this information in its own file. User defaults /plist will work for the case you described, though.

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