How to check if there is no server response in Objective c - ios

Question

I am trying to hit a web service . All works good. But if the server is not working then my app crashes .
How to handle NO SERVER RESPONSE .
Please help
Here is my code for hitting web service.
NSMutableDictionary *get = [[NSMutableDictionary alloc]init];
[get setObject:#"0" forKey:#"unit"];
NSData* jsonData = [NSJSONSerialization dataWithJSONObject:get options:kNilOptions error:nil];
NSString *jsonInputString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
NSString *post = [[NSString alloc]initWithFormat:#"req=%#",jsonInputString];
NSURL *url=[NSURL URLWithString:[NSString stringWithFormat:#"%#",getCommunity]];
NSData *postData = [post dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES];
NSString *postLength = [NSString stringWithFormat:#"%lu", (unsigned long)[postData length]];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:20.0];
[request setURL:url];
[request setHTTPMethod:#"POST"];
[request setValue:postLength forHTTPHeaderField:#"Content-Length"];
[request setValue:#"application/x-www-form-urlencoded" forHTTPHeaderField:#"Content-Type"];
[request setHTTPBody:postData];
NSError *error;
NSURLResponse *response;
NSData *responseData=[NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
if (responseData != nil) {
NSDictionary *jsonRecieveDict = (NSDictionary*)[NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:&error];
NSLog(#"jsonArray =======%#",jsonRecieveDict);
}
if (error)
{
UIAlertView *errorAlert = [[UIAlertView alloc]initWithTitle:#"Servor not responding" message:nil delegate:nil cancelButtonTitle:#"OK" otherButtonTitles:nil, nil];
[errorAlert show];
}
** ERROR IS BECAUSE OF INVALID STATUS CODE FROM SERVER **

Answer 1

if (error != nil) {
// Something went wrong...
NSLog(#"Servor not responding %#",error.description);
return;
}
if ([response statusCode] >= 300) {
NSLog(#"Servor not responding, status code: %ld", (long)[response statusCode]);
return;
}
First condition should be error checking,Second if response comes check the status code then only perform the remaining operation
Also change NSURLResponse *response; to NSHTTPURLResponse *response
OR diff Implementation
NSMutableDictionary *get = [[NSMutableDictionary alloc]init];
[get setObject:#"0" forKey:#"unit"];
if([NSJSONSerialization isValidJSONObject:get]){
//convert object to data
NSData* jsonData = [NSJSONSerialization dataWithJSONObject:newDatasetInfo options:kNilOptions error:nil];
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
[request setURL:[NSURL URLWithString:#"your url"]];
[request setHTTPMethod:#"POST"];
[request setValue:#"application/json" forHTTPHeaderField:#"Content-Type"];
[request setValue:#"application/json" forHTTPHeaderField:#"Accept"];
[request setHTTPBody:jsonData];
NSURLSessionConfiguration *config=[NSURLSessionConfiguration defaultSessionConfiguration];
NSURLSession *session=[NSURLSession sessionWithConfiguration:config];
NSURLSessionDataTask *task=[session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
if(response){
NSString *resp = [[NSString alloc] initWithBytes:[data bytes] length:[data length] encoding:NSUTF8StringEncoding];
NSLog(#"Echo %#",resp);
}
else{
NSLog(#"Timeout");
}
}];
[task resume];
}