NSDictionary 到 NSData
NSDictionary *myDictionary = [[NSDictionary alloc] initWithObjectsAndKeys:@"value1", @"key1", @"value2", @"key2", nil];
NSData *myData = [NSKeyedArchiver archivedDataWithRootObject:myDictionary];
保留路徑:
NSDictionary *myDictionary = (NSDictionary*) [NSKeyedUnarchiver unarchiveObjectWithData:myData];