Update NSFileProtection samples to set attributes on lock files

[kronik]

This issue is very similar to #1260 .
Application tries to select data from Realm db when app fetch in background handler is called.

And I

disabled protection at all:

+ (void)initialize {
    NSError *error = nil;
    NSURL   *fileUrl = [NSURL fileURLWithPath:[RLMRealm defaultRealmPath]];

    [fileUrl setResourceValue:@YES forKey:NSURLIsExcludedFromBackupKey error:&error];

    [[NSFileManager defaultManager] setAttributes:@{NSFileProtectionKey:NSFileProtectionNone}
                                     ofItemAtPath:[RLMRealm defaultRealmPath]
                                            error:&error];
}

tried also with NSFileProtectionCompleteUntilFirstUserAuthentication but still the same.

What I'm doing wrong?

[kronik]

I tried to compare behaviour with https://github.com/marcoarment/FCModel and FCModel works fine even in background locked mode.

[segiddins]

What sort of error are you seeing when realm crashes? It'd be really helpful if you could share a stack trace!

[kronik]

failed to open(). something related with permissions...

[kronik]

It seems like NSFileProtectionKey:NSFileProtectionNone needs to be applied to db log file or something else you guys use in addition to main db file.

[jpsim]

Hi @kronik, you're right that you'll have to set the NSFileProtection file attributes for the lock and log files if you're writing to the realm in the background.

NSString *pathToRealmFile = [RLMRealm defaultRealmPath];
NSArray *allRealmRelatedFiles = @[
  pathToRealmFile,
  [pathToRealmFile stringByAppendingPathExtension:@"lock"],
  [pathToRealmFile stringByAppendingPathExtension:@"log"],
  [pathToRealmFile stringByAppendingPathExtension:@"log_a"],
  [pathToRealmFile stringByAppendingPathExtension:@"log_b"]
];
for (NSString *path in allRealmRelatedFiles) {
  NSError *error = nil;
  [[NSFileManager defaultManager] setAttributes:@{NSFileProtectionKey: NSFileProtectionNone}
                                   ofItemAtPath:path
                                          error:&error];
}

We'll be updating our NSFileProtection related samples to reflect this as soon as possible.

[jpsim]

That's what we'll do in the short term. However users really shouldn't have to know about all these potential ancillary files so we'll be adding a convenience method like setFileProtectionKeyForRealmsAtPath:. We'll track this in a more flexible RLMConfiguration in #1584.

[alazier]

Lets just do #1584 rather than adding a new global configuration method that we will remove soon after adding.

[dismory]

Similarly, do I need to delete all these five files explicitly if I want to delete a Realm?

[tgoyne]

If you're just deleting and recreating the Realm file, then no (barring bugs in Realm).

[dismory]

If not, will it take more disk space?

[jpsim]

This is now documented in https://realm.io/docs/objc/latest/#encryption.