iCloud Support in an application for Mac OS X Lion

Question

Within a Mac OS X (10.7 Lion) Non-Document Based application, I want to include iCloud support so I can share data across other instances of the same application on other macs (not to iOS devices). After surfing around the Apple documentation a bit, I've discovered I should use a key value list storage in iCloud, as the document I want to upload contains only an array of custom objects (that have simple properties such as a name (string), date (date object), ...). This file is the only thing I want to upload to iCloud. Within the application, I have already implemented saving the file to the disk using NSFileManager's - (void)writeData:(NSData*)data toPath:(NSString *)path (or whatever it was, I've forgotten). It is loaded from the file using NSFileManager again (using - (NSData *)dataInFileAtPath:(NSString*)path, or whatever it was). The file is stored in a subdirectory, in the user's Application Support directory. It is saved whenever a new item is added to the array, or an item in the array is modified.

I was wondering if anyone could provide a link to a tutorial, or point me in the right direction, to writing that file to iCloud, then downloading it again on other instances of the same application? All the tutorials and documentation I have found have only been for iOS. Any help will be greatly appreciated!

Thanks in Advance!

Ben

Answer 1

Just use NSUbiquitousKeyValueStore, which is a lot like NSUserDefaults except that it's written to iCloud. You should read the iCloud Storage section of the Mac App Programming guide, but what you need to do may be as simple as enabling entitlements in the Summary tab of your App Target in Xcode, and then doing something like:

NSData *dataToStore = [NSKeyedArchiver dataWithRootObject:yourArray];
[[NSUbiquitousKeyValueStore defaultStore] setData:dataToStore forKey:@"yourKey"]; 

Then, to retrieve your data, just do

NSData *retrievedData = [[NSUbiquitousKeyValueStore defaultStore] dataForKey:@"yourKey"];
NSArray *retrievedArray = [NSKeyedUnarchiver unarchiveObjectWithData:retrievedData];

The one caveat here is that for this to work with an array of custom objects, these objects must all implement the NSCoding protocol. This is just a matter of implementing two methods; here's a good tutorial.

P.S. You use the same APIs whether you're developing for OS X or iOS, so there's no reason why you couldn't just follow an iOS tutorial for iCloud storage.