iOS app dev- NSMutableURLRequest is nil

Question

I am a new comer to iOS dev. Now I am faced with a weird problem. When I was running the following codes on iPhone 5 simulator, everything works fine. However, it doesn't work on my real iPhone 5. Can anybody do me a favour to help me find out the reason? OBJ-C: NSError *error;

NSMutableDictionary *dictionary = [[NSMutableDictionary alloc] init];
[dictionary setValue:@1 forKey:@"driverId"];
[dictionary setValue:@1 forKey:@"busId"];
[dictionary setValue:@1 forKey:@"lineId"];

NSData *postData = nil;
NSString *requestData = @"";
NSString *urlPath = @"myurl";
if([NSJSONSerialization isValidJSONObject:dictionary]){
    postData = [NSJSONSerialization dataWithJSONObject:dictionary options:NSJSONWritingPrettyPrinted error:nil];
    NSString *str = [[NSString alloc] initWithData:postData encoding:NSUTF8StringEncoding];
    requestData = [requestData stringByAppendingString:str];

    postData = [NSData dataWithBytes:[requestData UTF8String] length:[requestData length]];
}

NSString *postLength = [NSString stringWithFormat:@"%d", [postData length]];
NSURL *url = [NSURL URLWithString:urlPath];

NSMutableURLRequest *request=[NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0];
[request setValue:postLength forHTTPHeaderField:@"Content-Length"];
[request setHTTPMethod:@"POST"];
[request setHTTPBody:postData];

NSData *responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
NSString *response = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];

NSDictionary *responseDic = [NSJSONSerialization JSONObjectWithData:responseData options:NSJSONReadingMutableLeaves error:&error];
NSString *status = [responseDic objectForKey:@"status"];

By contrasting "request" with "nil", I found that request was nil.

The bug was:

2014-07-23 19:13:54.698 ShuttleBusForDriver[2958:60b] nil request 2014-07-23 19:13:54.699 ShuttleBusForDriver[2958:60b] responseDate: (null) 2014-07-23 19:13:54.701 ShuttleBusForDriver[2958:60b] * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'data parameter is nil' * First throw call stack: (0x2fc96ecb 0x3a431ce7 0x2fc96e0d 0x30624967 0xdfa55 0xde785 0x324cca33 0x324cc7f1 0x32658bf3 0x3257646f 0x32576279 0x32576211 0x324c82e5 0x3214431b 0x3213fb3f 0x3213f9d1 0x3213f3e5 0x3213f1f7 0x324cb99f 0x2fc61faf 0x2fc61477 0x2fc5fc67 0x2fbca729 0x2fbca50b 0x34b396d3 0x3252b871 0xdc69c 0xdc6d8 0x3a92fab7) libc++abi.dylib: terminating with uncaught exception of type NSException

Answer 1

@JingDu Your crash is happening because you are trying to decode a nil object to NSDictionary in this piece of code:

NSDictionary *responseDic = [NSJSONSerialization JSONObjectWithData:responseData options:NSJSONReadingMutableLeaves error:&error];
NSString *status = [responseDic objectForKey:@"status"];

Sometimes your urlconnection will timeout or server returns an error, which makes the responseData equals to nil. So you have to check if responseData exists or not. Do it like this:

if (responseData)
{
    NSDictionary *responseDic = [NSJSONSerialization JSONObjectWithData:responseData options:NSJSONReadingMutableLeaves error:&error];
    NSString *status = [responseDic objectForKey:@"status"];
}

By the way, you should post your symbolicated crash report to help others locate your issues quickly.

Please mark this answer as accepted if it fixes the crash. Thank you.