CODEWITHSUNDEEP
objective-cmacosuniqueuniqueidentifiernsdocument
kisileno
kisileno

Reputation: 787

NSDocument unique identifier

Q: Is there any way to acquire unique identifier of NSDocument in Document-based™ application which is persistent during app restarts?



Note1: there definitely should be some kind of id which is not just fileURL, but something else because app works well with autosaved and even not yet saved documents.

Note2: for some reasons I do not want to generate and persist this id to document's content file.

Upvotes: 4

Views: 328

Answers (2)

kisileno
kisileno

Reputation: 787

I ended up saving data into coder in a method encodeRestorableStateWithCoder during document closing and restoring that data in restoreDocumentWindowWithIdentifier when document is re-opened.

- (void) encodeRestorableStateWithCoder: (NSCoder *) coder {
    [super encodeRestorableStateWithCoder: coder];
    [coder encodeObject: @{@"color":@"red"} forKey: @"OBJECT_KEY"];
}

- (void) restoreDocumentWindowWithIdentifier: (NSString *) identifier
                                       state: (NSCoder *) state
                           completionHandler: (void (^) (NSWindow *, NSError *)) completionHandler {
    NSDictionary * restoredInfo = [state decodeObjectForKey: @"OBJECT_KEY"];
    [super restoreDocumentWindowWithIdentifier: identifier state: state completionHandler: completionHandler];
}

I think it is possible to save a generated UID there, but this storage might not be very reliable.

Upvotes: 0

Amin Negm-Awad
Amin Negm-Awad

Reputation: 16660

Even I did not try it, I think that extended attributes can do the job:

uuid_t uuid;
[[NSUUID new] getUUIDBytes:uuid];

int result = setxattr( path, "com.yourcompany.yourapp.yourattr", &uuid, sizeof(uuid), 0, 0);

Since extended attributes are nor part of the file itself neither a standard to all file systems, they can be lost, when the file is copied on storage with a file system that does not support such attributes.

Upvotes: 3

Related Questions