How to check if NSDictionary key is NULL

Question

I'm trying to check if an object exist for the key next_max_id in my JSON response dictionary. I've tried the following ways to check:

• if ([[pagination objectForKey:@"next_max_id"] isKindOfClass:[NSNull class]]) ...
• if ([pagination objectForKey:@"next_max_id"] == [NSNull class]) ...
• if ([pagination objectForKey:@"next_max_id"]) ...

However, when the pagination dictionary is empty i.e. (pagination = {};), I get these error messages:

-[NSNull objectForKey:]: unrecognized selector sent to instance ...
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSNull objectForKey:]: unrecognized selector sent to instance ...

How else can I check for if the object or rather the key exist, without a crash?

Updated: When the key next_max_id exist inside pagination, the JSON response would be like this

"pagination": {
    "next_url": "https://api.instagram.com/v1/tags/puppy/media/recent?access_token=fb2e77d.47a0479900504cb3ab4a1f626d174d2d&max_id=13872296",
    "next_max_id": "13872296"
}

Answer 1

if( [pagination objectForKey:@"your_key"] == nil ||  
    [[pagination objectForKey:@"your_key"] isEqual:[NSNull null]] ){
    //nil dictionary
}

Answer 2

With the error that you describe, pagination is not an NSDictionary, but pagination itself is an NSNull object. So the first check before everything else would be

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

That wouldn't happen if your JSON data contains "pagination": {} but it would happen if your JSON data contains "pagination": null .