iOS how to combine more than one option when writing NSData to file?

Question

I have the following method of saving file data with more than one option. I want to combine NSDataWritingAtomic with NSDataWritingFileProtectionComplete. Should I use the | symbol to combine two options when writing NSData?

The reason why I'm asking is that NSDataWritingFileProtectionComplete should not really work if the device has no passcode set, but I'm not seeing any difference, so I need to make sure I set the options correctly.

-(void)saveFileData:(NSData*)data
{
    NSError* error = nil;

   BOOL success = [data writeToFile:[self filepath] options:NSDataWritingAtomic|NSDataWritingFileProtectionComplete error:&error];

    if(success == NO || error != nil)
    {
        DLog(@"Error encrypting data file");
    }
}

score 0 · Answer 1 · answered Aug 22 '14 at 14:08

Yes, you're doing it correctly.

NSDataWritingFileProtectionComplete lets iOS know that it should use most restrictive protection class to encrypt your file. If device has passcode set this means that file will only be accessible when device is unlocked. If there's no passcode on the device then no such limitations will apply since there's no passcode to use for encryption.

When testing FileProtection-related code keep in mind that there when device is locked there's a short (10 seconds) grace period during which protected files are still accessible. This is done to ensure that apps working with such files have chance to transition to background state gracefully and complete any pending I/O.

iOS how to combine more than one option when writing NSData to file?

1 Answers1