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

Swift 4 version of @Travis M.'s answer;

class func removeNullFromJSONData(_ JSONData: Any) -> Any {
    if JSONData as? NSNull != nil {
        return JSONData
    }

    var JSONObject: Any!

    if JSONData as? NSData != nil {
        JSONObject = try! JSONSerialization.data(withJSONObject: JSONData, options: JSONSerialization.WritingOptions.prettyPrinted)
    }
    else {
        JSONObject = JSONData
    }

    if JSONObject as? NSArray != nil {
        let mutableArray: NSMutableArray = NSMutableArray(array: JSONObject as! [Any], copyItems: true)
        let indexesToRemove: NSMutableIndexSet = NSMutableIndexSet()

        for index in 0 ..< mutableArray.count {
            let indexObject: Any = mutableArray[index]

            if indexObject as? NSNull != nil {
                indexesToRemove.add(index)
            }
            else {
                mutableArray.replaceObject(at: index, with: removeNullFromJSONData(indexObject))
            }
        }

        mutableArray.removeObjects(at: indexesToRemove as IndexSet)

        return mutableArray;
    }
    else if JSONObject as? NSDictionary != nil {
        let mutableDictionary: NSMutableDictionary = NSMutableDictionary(dictionary: JSONObject as! [AnyHashable : Any], copyItems: true)

        for key in mutableDictionary.allKeys {
            let indexObject: Any = mutableDictionary[key] as Any

            if indexObject as? NSNull != nil {
                mutableDictionary.removeObject(forKey: key)
            }
            else {
                mutableDictionary.setObject(removeNullFromJSONData(indexObject), forKey: key as! NSCopying)
            }
        }

        return mutableDictionary
    }
    else {
        return JSONObject
    }
}