Asynchronous NSURLConnection request responds multiple times - iphone

Question

I am facing weired issue. I am sending Asynchronus NSUrlrequest call but in return i am getting multiple time responde with some part of json
can someone please help me with what I did wrong.
code
NSString *_query = #"http://abc.com/index.php";
NSData *myRequestData = [NSData dataWithBytes:[_requestString UTF8String]
length:[_requestString length]];
__block NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:_query]];
[request setHTTPMethod: #"POST" ];
[request setValue:#"application/x-www-form-urlencoded" forHTTPHeaderField:#"content-type"];
[request setHTTPBody: myRequestData ];
[[NSURLConnection alloc] initWithRequest:request delegate:self];
NSRunLoop *runLoop = [NSRunLoop currentRunLoop];
[runLoop addTimer:timeOutTimer forMode:NSDefaultRunLoopMode];
Response
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
// check is response is a valid JSON?
NSError *error;
id jsonObj = [NSJSONSerialization JSONObjectWithData: data options:kNilOptions error:&error];
BOOL isValid = [NSJSONSerialization isValidJSONObject:jsonObj];
NSString *content = [[NSString alloc] initWithData:data
encoding:NSUTF8StringEncoding];
NSLog(#"Content: %#",content);
if (isValid)
{
NSDictionary *data = [content JSONValue];
}
[content release];
}

Answer 1

As data is received by the client, this callback gets called:
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
didReceiveData is giving you data as it's receiving it and can be called multiple times with chunks of the data.
From the NSURLConnection docs:
The delegate is periodically sent connection:didReceiveData: messages
as the data is received. The delegate implementation is responsible
for storing the newly received data.
From those docs:
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
// Append the new data to receivedData.
// receivedData is an instance variable declared elsewhere.
[receivedData appendData:data];
}
When its all done, connectionDidFinishLoading will get called and your appended data is ready for you to use.
Finally, if the connection succeeds in downloading the request, the
delegate receives the connectionDidFinishLoading: message. The
delegate will receive no further messages for the connection and the
NSURLConnection object can be released.