Question

In Cocoa, you can get the attributes of a file as follow

NSString *path = @"/path/to/some/file";
NSError *err = ......;
NSDictionary *dic = [[NSFileManager defaultManager] attributesOfItemAtPath:path error:&err];
NSLog(@"%@", dic);

And it will return a directory of keys, for example

{
    NSFileCreationDate = "2009-12-02 10:03:38 +0000";
    NSFileExtensionHidden = 0;
    NSFileGroupOwnerAccountID = 80;
    NSFileGroupOwnerAccountName = admin;
    NSFileHFSCreatorCode = 0;
    NSFileHFSTypeCode = 0;
    NSFileModificationDate = "2009-12-02 19:20:54 +0000";
    NSFileOwnerAccountID = 501;
    NSFileOwnerAccountName = Tony;
    NSFilePosixPermissions = 511;
    NSFileReferenceCount = 1;
    NSFileSize = 496988;
    NSFileSystemFileNumber = 5187496;
    NSFileSystemNumber = 234881029;
    NSFileType = NSFileTypeRegular;
}

Now, you can also use the CoreFoundation MDItem to get file attributes

NSString *path = @"/path/to/some/file";
MDItemRef mdItem = MDItemCreate(kCFAllocatorDefault, (__bridge CFStringRef)path);
CFArrayRef arr = MDItemCopyAttributeNames(mdItem);
CFDictionaryRef dic = MDItemCopyAttributes(mdItem, arr);
NSLog(@"%@", dic);

And it will return something like this

{
    kMDItemAuthors =     (
        "Some One"
    );
    kMDItemContentCreationDate = "2009-12-02 10:03:38 +0000";
    kMDItemContentModificationDate = "2009-12-02 19:20:54 +0000";
    kMDItemContentType = "org.openxmlformats.presentationml.presentation";
    kMDItemContentTypeTree =     (
        "org.openxmlformats.presentationml.presentation",
        "org.openxmlformats.openxml",
        "public.zip-archive",
        "com.pkware.zip-archive",
        "public.data",
        "public.item",
        "com.apple.bom-archive",
        "public.archive",
        "public.presentation",
        "public.composite-content",
        "public.content"
    );
    kMDItemDateAdded = "2011-08-16 07:52:53 +0000";
    kMDItemDisplayName = "Some File.pptx";
    kMDItemFSContentChangeDate = "2009-12-02 19:20:54 +0000";
    kMDItemFSCreationDate = "2009-12-02 10:03:38 +0000";
    kMDItemFSCreatorCode = 0;
    kMDItemFSFinderFlags = 0;
    kMDItemFSHasCustomIcon = 0;
    kMDItemFSInvisible = 0;
    kMDItemFSIsExtensionHidden = 0;
    kMDItemFSIsStationery = 0;
    kMDItemFSLabel = 0;
    kMDItemFSName = "Some File.pptx";
    kMDItemFSNodeCount = 496988;
    kMDItemFSOwnerGroupID = 80;
    kMDItemFSOwnerUserID = 501;
    kMDItemFSSize = 496988;
    kMDItemFSTypeCode = 0;
    kMDItemKind = "Microsoft PowerPoint presentation";
    kMDItemLogicalSize = 496988;
    kMDItemPhysicalSize = 499712;
    kMDItemTitle = "PowerPoint Presentation";
}

My question is, what’s the difference between these two methods of finding file attributes? There seem to be some equivalence but not all the time, which is better? And why are there these two ways anyways?

Answer 1

The attributes returned from NSFileManager are attributes stored on the file in the filesystem. The results from MDItemCopyAttributes are from the Spotlight index which includes most (all?) of the filesystem attributes as well as the results from any of the Spotlight plugins installed on the system.