Checking a Null Value in Objective-C That Has Been Returned from a JSON String

Checking a null value in Objective-C that has been returned from a JSON string

<null> is how the NSNull singleton logs. So:

if (tel == (id)[NSNull null]) {
    // tel is null
}

(The singleton exists because you can't add nil to collection classes.)

Checking a null value from Json response in Objective-C

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{

    NSError *error;
    json = [NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:&error];
    NSLog(@"json.... %@",json);

    id jsonObject = [NSJSONSerialization JSONObjectWithData:responseData options:NSJSONReadingAllowFragments error:nil];

    NSLog(@"jsonObject=%@", jsonObject);

    NSDictionary *checkArray=[json valueForKey:@"ND"];

    NSArray *tel = [checkArray valueForKey:@"FN"];

    for (id photo in tel)
    {
        if (photo == [NSNull null])
        {
            // photo is null

        }
        else
        {
            // photo isn't null. It's an array
            NSArray *innerPhotos = photo;
            NSLog(@"photo... %@",innerPhotos);
        }

    }

    cheDisk1=[checkArray valueForKey:@"LN"];

    NSLog(@"FN =%@",tel);

    [ContactTableview reloadData];

}

Checking a null value from Json response in Objective-C

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{

    NSError *error;
    json = [NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:&error];
    NSLog(@"json.... %@",json);

    id jsonObject = [NSJSONSerialization JSONObjectWithData:responseData options:NSJSONReadingAllowFragments error:nil];

    NSLog(@"jsonObject=%@", jsonObject);

    NSDictionary *checkArray=[json valueForKey:@"ND"];

    NSArray *tel = [checkArray valueForKey:@"FN"];

    for (id photo in tel)
    {
        if (photo == [NSNull null])
        {
            // photo is null

        }
        else
        {
            // photo isn't null. It's an array
            NSArray *innerPhotos = photo;
            NSLog(@"photo... %@",innerPhotos);
        }

    }

    cheDisk1=[checkArray valueForKey:@"LN"];

    NSLog(@"FN =%@",tel);

    [ContactTableview reloadData];

}

Identify NULL values in objective C

Foundation collections can only contain objects types (NSObject subclasses). As such, in order to represent nil we use +[NSNull null]. It just so happens that NSNull's implementation of -description returns <null> and that's what you're seeing in the console.

Try comparing the result of -objectForKey to [NSNull null] instead.

how to check for null object returned in xcode

A JSON "null" value is converted to [NSNull null], which you can check
for with

if (text == [NSNull null]) ...

because it is a singleton.

Alternatively, you can check if the object contains the expected type, i.e. a string:

NSString *text = [obj objectForKey:@"BillingStreet"];
if ([text isKindOfClass:[NSString class]]) {
    self.labelCustomerAddress.text = text;
} else {
    self.labelCustomerAddress.text = @"no street";
}

This is more robust in the case that a server sends bad data, e.g. a number or an array instead of a string.

How can I check If I got null from json?

I believe most JSON parsers represent null as [NSNull null].

Considering jsonDict points to that single element in the array, then the following should work:

if ([jsonDict objectForKey:@"photo"] == [NSNull null]) {
    // it's null
}

---

Edit based on comment: so jsonDict, despite its name, is an array. In that case, rename jsonDict to jsonArray to avoid further confusion. Then, considering jsonArray points to an array similar to the example posted in the question:

NSArray *photos = [jsonArray valueForKey:@"photo"];
for (id photo in photos) {
    if (photo == [NSNull null]) {
        // photo is null
    }
    else {
        // photo isn't null
    }
}

---

Further edit based on OP’s modified question:

NSArray *jsonArray = [string JSONValue];

NSArray *photos = [jsonArray valueForKey:@"photo"];
for (id photo in photos) {
    if (photo == [NSNull null]) {
        // photo is null
    }
    else {
        // photo isn't null. It's an array
        NSArray *innerPhotos = photo;
        …
    }
}

How do I test for null in NSDictionary from SBJSON?

When transferring data from JSON to a Cocoa collection, the NSNull class is used to represent "no value", since Cocoa collections can't have empty slots. <null> is how NSNull prints itself.

To test for this, you can use someObject == [NSNull null]. It's a singleton -- there's only one instance of NSNull per process -- so pointer comparison works, although you may prefer to follow the usual Cocoa comparison convention and use [someObject isKindOfClass:[NSNull class]].

You're getting the crash because you're sending integerValue to that NSNull object. NSNull doesn't respond to integerValue and raises an exception.

Parsing Json to object giving null Value

I got the very perfect solution for your question which works fine now.Please check the below answer

- (void)callAPI 
{

  NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];
  [request setHTTPMethod:@"GET"];
  [request setURL:[NSURL URLWithString:@"https://dl.dropboxusercontent.com/s/2iodh4vg0eortkl/facts.json"]];
  [[[NSURLSession sharedSession] dataTaskWithRequest:request completionHandler:
  ^(NSData * data,
    NSURLResponse * response,
    NSError * error) {
      NSString *jsonString = [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding];
      NSLog(@"jsonString is: %@", jsonString);
      NSData *dataCon = [jsonString dataUsingEncoding:NSUTF8StringEncoding];
      id jsonVal = [NSJSONSerialization JSONObjectWithData:dataCon options:0 error:nil];
      if([jsonVal isKindOfClass:[NSDictionary class]]) {
          NSLog(@"The response starts with NSDictionary");
          NSArray *arrJsonVal = [jsonVal objectForKey:@"rows"];
          NSMutableArray *arrTitle = [[NSMutableArray alloc]init];
          NSMutableArray *arrDesc = [[NSMutableArray alloc]init];
          NSMutableArray *arrImage = [[NSMutableArray alloc]init];
          for(NSDictionary *dict in arrJsonVal) {
              NSString *strTitle = [dict objectForKey:@"title"];
              NSString *strDesc = [dict objectForKey:@"description"];
              NSString *strImage = [dict objectForKey:@"imageHref"];

              [arrTitle addObject:strTitle];
              [arrDesc addObject:strDesc];
              [arrImage addObject:strImage];
          }
          NSLog(@"arrTitle is - %@",arrTitle);
          NSLog(@"arrDesc is - %@",arrDesc);
          NSLog(@"arrImage is - %@",arrImage);

      }else {
          NSLog(@"The response starts with NSArray");
      }
  }] resume];

}

The Printed results are

After that

Then Array results are

Finally the results are

swift how can I check for NULL values coming from Json

You just need to conditionally cast your dictionary value to String and use the Nil Coalescing Operator ?? to assign "0" in case of failure null:

let vote_status = Stream["vote_status"] as? String ?? "0"

Condition for checking NOT null value for NSString in Objective C

Try the following code

id phoneNo = [personDict objectForKey:kPhoneKey];

if( phoneNo && ![phoneNo isKindOfClass:[NSNull class]] )
{
    NSString *tempPhone = [NSString stringWithFormat:@"%@", [personDict objectForKey:kPhoneKey]];
    NSLog(@"NSString *tempPhone = %@",tempPhone);
}
else
{
    NSLog(@"NSString *tempPhone is null");
}

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