Question

I am allowing for application data (it’s a Mac app on 10.7) to be exported as an XML file, and one field I would like to be able to export/import to/from XML is an NSData field. What would be the correct/accepted way of doing this? Should I convert to base64 and write that string to XML?

I would prefer not to roll my own solution, using a category, as the accepted answer to the linked question does (linking to Matt Gallagher’s solution).

Update

I just discovered the NSPropertyListSerialization class. I got my hopes up, but it only has static serialization methods which return NSData representations.

Answer 1

I realized (as my updated alluded to) that I could use the NSPropertyListSerialization class, since the NSData returned by -dataWithPropertyList:format:options:error: is just a UTF-8 string. This is what I’m using to serialize:

NSData *data = value;

NSError *error = nil;
NSData *plistData = [NSPropertyListSerialization dataWithPropertyList:data
                                                               format:NSPropertyListXMLFormat_v1_0
                                                              options:0
                                                                error:&error];
if (error) {
    NSLog(@"Error serializing data to plist XML: %@", error);
} else {
    NSString *plistString = [[NSString alloc] initWithData:plistData encoding:NSUTF8StringEncoding];
    NSXMLElement *dataElement = [NSXMLElement elementWithName:field
                                                  stringValue:plistString];
}

And deserialize:

NSData *plistData = [element.stringValue dataUsingEncoding:NSUTF8StringEncoding];
NSData *originalData = [NSPropertyListSerialization propertyListWithData:plistData
                                                                 options:NSPropertyListImmutable
                                                                  format:NULL
                                                                   error:&error];

if (error) {
    NSLog(@"Error deserializing data from plist XML: %@", error);
} else {
    value = originalData;
}