I want to archive a dictionary containing just NSStrings, but when I unarchive, an error occurred:

> 
> [NSKeyedUnarchiver initForReadingWithData:]: non-keyed archive cannot be decoded by NSKeyedUnarchiver
> 
> 
> 

My code is:

```
- (IBAction)startArchive:(id)sender {
    NSString *path = [self pathForDataFile];
    NSMutableDictionary *ageDictionary= [NSMutableDictionary dictionary];
    [ageDictionary setValue:@"12" forKey:@"Jack"];
    [ageDictionary setValue:@"22" forKey:@"John"];
    [NSArchiver archiveRootObject:ageDictionary toFile:path];
}

- (IBAction)unarchive:(id)sender {
    NSString *path = [self pathForDataFile];
    NSDictionary *rootObject = [NSKeyedUnarchiver unarchiveObjectWithFile:path];
    NSLog(@"%@",rootObject);
}

```