URLConnection sendSynchronousRequest Question?

I am making a synchronous call to the web service and sometimes I get the correct result back from the web service and sometimes I get HTML result indicating a Runtime error. Is there anything on the iOS side I have to do to correctly call the web service. Here is my code:

NSURLResponse *response = nil; 
NSError *error = nil;         
NSString *requestString = @"some parameters!";        
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url];

[request addValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];        
[request setHTTPMethod:@"POST"];
[request setHTTPBody:[requestString dataUsingEncoding:NSUTF8StringEncoding]];

NSData *data = [NSURLConnection sendSynchronousRequest:request 
                                     returningResponse:&response 
                                                 error:&error];    
NSString *responseData = [[NSString allo开发者_JS百科c] initWithData:data 
                                               encoding:NSUTF8StringEncoding];

Is it because I am not releasing properly?

you have to set the delegate methods of urlconnection like this

NSMutableURLRequest* urlRequest = [[NSMutableURLRequest alloc] initWithURL:url];
 [urlRequest setHTTPMethod:@"POST"];
 urLConnection=[[NSURLConnection alloc] initWithRequest:urlRequest delegate:self];

and the following delegate methods do the trick

    - (void)connection:(NSURLConnection*)connection didReceiveResponse:(NSURLResponse*)response {
    NSHTTPURLResponse* httpResponse = (NSHTTPURLResponse*)response;
    [receivedData setLength:0];
}

-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data  
{

    [receivedData appendData:data];

}  

you will receive error in the following delegate if connection fails

  - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{}

you better get the response from the finished connection which tells that all the data been received

    - (void)connectionDidFinishLoading:(NSURLConnection *)connection  
{  
recievedData //the complete data 
}

try this

    NSError * error;
NSURLResponse * urlresponse;

NSURL * posturl=[NSURL URLWithString:@"Type your webService URL here"];

NSMutableURLRequest * request=[[NSMutableURLRequest alloc]initWithURL:posturl cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:50];

[request setHTTPMethod:@"POST"];
[request addValue:@"application/x-www-form-urlencoded; charset=utf-8" forHTTPHeaderField:@"Content-Type"];

NSString * body=[NSString stringWithFormat:@"fbid=%@",userid];
[request setHTTPBody:[body dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES]];

NSData * data=[NSURLConnection  sendSynchronousRequest:request returningResponse:&urlresponse error:&error];

if (data==nil) {
    return;
}

id jsonResponse=[NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:&error];
NSLog(@" json response %@", jsonResponse);
if (![[jsonResponse objectForKey:@"code"] isEqualToNumber:[NSNumber numberWithInt:200]]) {
    NSLog( @" successFull ");

this method works for me for more information read facebook documents for ios login

//set request    
NSURLRequest *req=[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://indianbloodbank.com/api/donors/?bloodgroup=O%2B"]];

NSLog(@"Request-%@",req);

NSError *err=nil;
NSURLResponse *res=nil;

NSData *xmldata=[NSURLConnection sendSynchronousRequest:req returningResponse:&res error:&err];

NSLog(@"Error-%@",err);
NSLog(@"Response-%@",res);
NSLog(@"XmlData-%@",xmldata);

xmldictionary=[XMLReader dictionaryForXMLData:xmldata error:&err];

NSLog(@"XmlDictionary-%@",xmldictionary);

mArray=[xmldictionary retrieveForPath:@"response.donorslist.donors"];

NSLog(@"MutableArray-%@",mArray);

lblname.text=[[mArray objectAtIndex:0]valueForKey:@"name"];
lbllocation.text=[[mArray objectAtIndex:0]valueForKey:@"location"];
lblphone.text=[[mArray objectAtIndex:0]valueForKey:@"phone"];

NSLog(@"%@,%@,%@",lblname.text,lbllocation.text,lblphone.text);
NSLog(@"%@",mArray);

For loop:

for (int i=0; i<mArray.count; i++)
{
    Data * don=[NSEntityDescription insertNewObjectForEntityForName:@"Data" inManagedObjectContext:app.managedObjectContext];

    don.donorid=[[mArray objectAtIndex:i]valueForKey:@"id"];
    don.gender=[[mArray objectAtIndex:i]valueForKey:@"gender"];
    don.name=[[mArray objectAtIndex:i]valueForKey:@"name"];
    don.location=[[mArray objectAtIndex:i]valueForKey:@"location"];
    don.phone=[[mArray objectAtIndex:i]valueForKey:@"phone"];

    [app saveContext];

    NSLog(@"%@,%@,%@,%@,%@",[[mArray objectAtIndex:i]valueForKey:@"id"],[[mArray objectAtIndex:i]valueForKey:@"gender"],[[mArray objectAtIndex:i]valueForKey:@"name"],[[mArray objectAtIndex:i]valueForKey:@"location"],[[mArray objectAtIndex:i]valueForKey:@"phone"]);

}