Implementing iTunes syncing and a lesson to always run unit tests.

So the latest version of my main app is in the app store and…. it has a minor minor bug.  In a rush to eliminate a highly unlikely, in fact to pre-empt, a bug I updated some code to check for the possibility of NSNull being assigned to an NSString.  For some reason this changed the md5 sum assigned to two recipes (Shepherd’s Pie and Seafood Linguine Carbonara) which means they will be duplicated for every user I expect.  Shame.  Not life ending but annoying.  I submitted the update metadata around 21:20 on Friday, the app at around 21:57.  I fixed the bug at 21:45.  I didn’t run the OCUnit tests which would have spotted the md5 checksum changing when it should not have.

Easy to fix though and on the upside all of this code and unit tests means development is much faster now.  So I’m well on the way to iTunes document synchronisation support.  I’ve had to relocate a plist file and the sqlite database out of documents and into library otherwise they show up in iTunes.  So all you people that write core data tutorials putting sqlite in the documents folder… stop it!  It’s not a good idea use NSLibraryDirectory instead of NSDocumentDirectory when calling NSSearchPathForDirectoriesInDomains.

On another note, to determine what files were new in the documents folder I thought I’d use file info, like dates etc.  Figuring that when the file is written to the iPhone by iTunes it would write a new file but it doesn’t… it preserves the host machines modified and creation dates:

      NSDictionary *fileInfo = [[NSFileManager defaultManager] attributesOfItemAtPath:filePath
      NSDate *lastModified = [fileInfo valueForKey:NSFileModificationDate];

(gdb) po fileInfo
    NSFileCreationDate = "2011-05-09 11:30:53 +0000";
    NSFileExtensionHidden = 0;
    NSFileGroupOwnerAccountID = 501;
    NSFileGroupOwnerAccountName = mobile;
    NSFileModificationDate = "2011-05-09 11:30:53 +0000";
    NSFileOwnerAccountID = 501;
    NSFileOwnerAccountName = mobile;
    NSFilePosixPermissions = 420;
    NSFileProtectionKey = NSFileProtectionNone;
    NSFileReferenceCount = 1;
    NSFileSize = 1788192;
    NSFileSystemFileNumber = 2608135;
    NSFileSystemNumber = 234881027;
    NSFileType = NSFileTypeRegular;

A shame but totally understandable as the file is not being modified or created as such. Looks like I’ll need to track a bit more metadata myself or waste time import/exporting everything every time. Err… no.

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