iOS: TouchJSON & retrieved data size - ios

Question

I want to display a UIProgressView indicating the amount of data received as I request JSON data using touchJSON. I was wondering if there was a way to listen to the size of the data being received.
I request data using the following:
- (NSDictionary *)requestData
{
NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:apiURL]];
NSError *error = nil;
NSDictionary *result = [[CJSONDeserializer deserializer] deserializeAsDictionary:data error:&error];
if(error != NULL)
NSLog(#"Error: %#", error);
return result;
}

Answer 1

You will have to introduce some more code to include a download status indicator bar. At the moment you download the data with [NSData dataWithConentsOfURL:...]. Instead, you will make a class that uses a NSURLConnection object to download data, accumulate that data in an MSMutableData object, and update your UI accordingly. You should be able to use the ContentLength HTTP header and the - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data; updates to determine the status of the download.
Here are some relevant methods:
- (void) startDownload
{
downloadedData = [[NSMutableData alloc] init];
connection = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:YES];
}
- (void)connection:(NSURLConnection *)c didReceiveResponse:(NSURLResponse *)response
{
totalBytes = [response expectedContentLength];
}
// assume you have an NSMutableData instance variable named downloadedData
- (void)connection:(NSURLConnection *)c didReceiveData:(NSData *)data
{
[downloadedData appendData: data];
float proportionSoFar = (float)[downloadedData length] / (float)totalBytes;
// update UI with proportionSoFar
}
- (void)connection:(NSURLConnection *)c didFailWithError:(NSError *)error
{
[connection release];
connection = nil;
// handle failure
}
- (void)connectionDidFinishLoading:(NSURLConnection *)c
{
[connection release];
connection = nil;
// handle data upon success
}
Personally, I think the simplest way to do this is to create a class that implements the above methods to do generic data downloads and interface with that class.
This should be enough to get you what you need.