How To Handle If Response Is nil, in objective-c

All,

How to handle if the response is nil.

if response do have any network issue it provided me string format.

    if ([response isKindOfClass:[NSString class]]) {
    // print response .
    }
    //on successfully response, which provided dictionary, 
check for key success which do have true or false.
    else if ([[response objectForKey:@"success"] boolValue] == true) {
    // on true print response data.
    }

    //on success response, with failure message which is false.
    else if ([[response objectForKey:@"success"] boolValue] == false) {
    // handle error on success is false.
    }

Here my question comes,if make response to nil response = nil; how to handle if response is nil? and satisfy the above the conditions also.

since manually i set response data is nil.

id response = nil; it trigger the below condition also.

else if ([[response objectForKey:@"success"] boolValue] == false) {
// handle error on success is false.
}

@All Thanks in Advance.