Objective-c way of serializing arrays that contain different types

Question

Hello,

My NSMutableArray instance contains instances of different types of objects that have common ancestor. I want to serialize the array, but NSKeyedArchiver class seems to archive arrays contain certain types of objects. Is there an easy way to to this with stock serialization classes ?

Answer 1

I don't think NSKeyedArchiver is your problem, since it doesn't know about arrays or anything. Perhaps you need to implement the NSCoding protocol on each subclass?

Edit:

Not sure how you're using your NSKeyedArchiver, but this is how you should use it:

NSMutableData *data = [NSMutableData new];
NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
[archiver encodeObject:array forKey:@"array"];
[data writeToFile:filename attomically:YES];
[archiver release];
[data release];

And to read it in later:

NSData *data = [[NSData alloc] initWithContentsOfFile:filename];
NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
array = [[unarchiver objectForKey:@"array"] retain];
[unarchiver release];
[data release];

This assumes that array is some type of NSObject, including NSArray, NSSet, NSDictionary, etc, or any of their mutable equivalents.