Question

I trie to check if the returned value from objectForKey is not NULL

if([[fbResult objectForKey:@"current_location"]objectForKey:@"country"])
formViewController.country=[[fbResult objectForKey:@"current_location"]objectForKey:@"country"];

But i have an error on the first line

UPDATE

fbResult is a JSON string,if the user has puted ​​his city and his country in facebook it look like :

 "birthday_date" = "07/*****9";
    "contact_email" = "***[e-mail]";
    "current_location" =     {
        city = Tunis;
        country = Tunisia;
        id = 11166369***;
        name = "Tunis, Tunisia";
        state = Qabis;
        zip = "";
    };
    locale = "fr_FR";
    name = "Mehdi ****el";
    pic = "https://fbcdn-profile-a.akamaihd.net/hprofile-********_s.jpg";
    sex = male;
    uid = 530****;
}

and if the user did not put his country and city it look like :

   { "birthday_date" = "02/*3/19**";
        "contact_email" = "kev**[e-mail]";
        "current_location" = "<null>";
        locale = "fr_FR";
        name = "Aude ***";
        pic = "http://profile.ak.fbcdn.net/hprofile-ak-snc4/4***2_**8_1112_s.jpg";
        sex = female;
        uid = 11***04*;
    }

error is

-[NSObject(NSObject) doesNotRecognizeSelector:] + 96

Answer 1

Checking for existence of an object within a dictionary that is nested in another dictionary is not going to catch all occurrences of bad data.

To make your code more solid

id current_location = [fbResult objectForKey:@"current_location"];
if (current_location != nil && [current_location class] != [NSNull class]) {

    id country = [current_location objectForKey:@"country"];
    if (country != nil) {
        formViewController.country= country;
    } else {
        // current_location has no country
    } 

} else {
    // fbResult has no current_location
}

If the current_location is supposed to be a dictionary you can swap out id currentLocation with NSDictionary * currentLocation

from your update, your current_location can potentially be an instance of NSNull

you can check against that with

[yourObject class] != [NSNull class]