Swift Static method used to remove nulls from dictionaries

DictionaryUtils.swift

import Foundation

class DictionaryUtils {
    class func removeNullsFromDictionary(origin:[String:AnyObject]) -> [String:AnyObject] {
        var destination:[String:AnyObject] = [:]
        for key in origin.keys {
            if origin[key] != nil && !(origin[key] is NSNull){
                if origin[key] is [String:AnyObject] {
                    destination[key] = self.removeNullsFromDictionary(origin[key] as! [String:AnyObject])
                } else if origin[key] is [AnyObject] {
                    let orgArray = origin[key] as! [AnyObject]
                    var destArray: [AnyObject] = []
                    for item in orgArray {
                        if item is [String:AnyObject] {
                            destArray.append(self.removeNullsFromDictionary(item as! [String:AnyObject]))
                        } else {
                            destArray.append(item)
                        }
                    }
                } else {
                    destination[key] = origin[key]
                }
            } else {
                destination[key] = ""
            }
        }
        return destination
    }
    
}