Removing nulls from a JSON structure recursively

Question

I\'m frequently finding the need to cache data structures created by NSJSONSerialization to disk and as -writeToFile fails if there are nulls, I ne

Answer 1

Here's the code I'm using to clean up my JSON calls, seems to work well but, since there's some processing overhead involved I really only use it in situations where I can't do the null handling on the server. NSNull crashes is far and away our biggest app crash problem.

+ (id)cleanJsonToObject:(id)data {
    NSError* error;
    if (data == (id)[NSNull null]){
        return [[NSObject alloc] init];
    }
    id jsonObject;
    if ([data isKindOfClass:[NSData class]]){
        jsonObject = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error];
    } else {
        jsonObject = data;
    }
    if ([jsonObject isKindOfClass:[NSArray class]]) {
        NSMutableArray *array = [jsonObject mutableCopy];
        for (int i = array.count-1; i >= 0; i--) {
            id a = array[i];
            if (a == (id)[NSNull null]){
                [array removeObjectAtIndex:i];
            } else {
                array[i] = [self cleanJsonToObject:a];
            }
        }
        return array;
    } else if ([jsonObject isKindOfClass:[NSDictionary class]]) {
        NSMutableDictionary *dictionary = [jsonObject mutableCopy];
        for(NSString *key in [dictionary allKeys]) {
            id d = dictionary[key];
            if (d == (id)[NSNull null]){
                dictionary[key] = @"";
            } else {
                dictionary[key] = [self cleanJsonToObject:d];
            }
        }
        return dictionary;
    } else {
        return jsonObject;
    }
}

You call it by passing the NSData retrieved via NSURLConnection.

NSArray *uableData = [utility cleanJsonToObject:data];

or

NSDictionary *uableData = [utility cleanJsonToObject:data];