loading big xml file - objective-c

Question

i'm trying to load big file from server, but when it's loading always very slow.
Can you suggest me method, how to fast load more, then 200k objects ?
Printing description of data:
(NSData *) data = 0x08e51d80 151341098 bytes
NSURLRequest *urlRequest = [NSURLRequest requestWithURL:url];
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
[NSURLConnection sendAsynchronousRequest:urlRequest queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
{
if (error)
{
NSLog(#"Error,%#", [error localizedDescription]);
}
else
{
NSLog(#"%#", [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding]);
}
}];

Answer 1

Two points:
You can use file output stream for network request instead of holding the whole NSData in memory. For example, AFNetworking supports such option.
You can use a SAX parser with stream support for deserialising your data from file, to, again, avoid loading whole XML into memory. For example, NSXMLParser does support stream parsing.
Here's the example of setting up NSXMLParser:
NSInputStream *fileStream = [NSInputStream inputStreamWithURL:temporaryXMLFileURL];
NSXMLParser *parser = [[NSXMLParser alloc] initWithStream:fileStream];
parser.delegate = yourParserDelegate;
BOOL result = [parser parse];
You can implement your parsing & object instantiation code in a class adopting NSXMLParserDelegate, there're a lot of examples over the internet, even one from Apple.
Please keep in mind that all this tricks won't speed up downloading of your large file from the internet, it depends entirely on your connection speed. My approach would only help to reduce your application memory footprint (hence reducing the risk of your app being jettisoned by iOS because of memory pressure).

Answer 2

Switch to JSON. JSON will load and parse MUCH faster than XML. I have a JSON file that is 1.8 MB and it downloads and parses (I use AFNetworking for the connection) in around 7 seconds. Another tip, cache the resulting NSArray on the device so that the next time, you can load directly from that cached array and in the background request the file again and compare to the cached Array. If different, update the model with the new data.
Something like this:
NSURLRequest *urlRequest = [NSURLRequest requestWithURL:url];
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
[NSURLConnection sendAsynchronousRequest:urlRequest queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
if (!error) {
NSError *error = nil;
id jsonObj = [NSJSONSerialization JSONObjectWithData:responseData options:0 error:&error];
}
}
else {
NSLog(#"Error,%#", [error localizedDescription]);
}
}];