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

Question

I have a JSON object that is coming from a webserver.

The log is something like this:

{          
   "status":"success",
   "UserID":15,
   "Name":"John",
   "DisplayName":"John",
   "Surname":"Smith",
   "Email":"email",
   "Telephone":null,
   "FullAccount":"true"
}

Note the Telephone is coming in as null if the user doesn't enter one.

When assigning this value to a NSString, in the NSLog it's coming out as <null>

I am assigning the string like this:

NSString *tel = [jsonDictionary valueForKey:@"Telephone"];

What is the correct way to check this <null> value? It's preventing me from saving a NSDictionary.

I have tried using the conditions [myString length] and myString == nil and myString == NULL

Additionally where is the best place in the iOS documentation to read up on this?

Answer 1

<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.)