Groundup JSON Stringify in swift

MyJSONStringify.swift

func jsonStringify(jsonObject: AnyObject) -> String {
    
    var jsonString: String = ""
    
    switch jsonObject {
        
        case _ as [String: AnyObject] :
            
            let tempObject: [String: AnyObject] = jsonObject as! [String: AnyObject]
            jsonString += "{"
            for (key , value) in tempObject {
                if jsonString.characters.count > 1 {
                    jsonString += ","
                }
                jsonString += "\"" + String(key) + "\":"
                jsonString += jsonStringify(value)
            }
            jsonString += "}"

        case _ as [AnyObject] :
            
            jsonString += "["
            for i in 0..<jsonObject.count {
                if i > 0 {
                    jsonString += ","
                }
                jsonString += jsonStringify(jsonObject[i])
            }
            jsonString += "]"
            
        case _ as String :
            
            jsonString += ("\"" + String(jsonObject) + "\"")
            
        case _ as NSNumber :
            
            if jsonObject.isEqualToValue(NSNumber(bool: true)) {
                jsonString += "true"
            } else if jsonObject.isEqualToValue(NSNumber(bool: false)) {
                jsonString += "false"
            } else {
                return String(jsonObject)
            }
            
        case _ as NULL :
            
            jsonString += "null"
            
        default :
            
            jsonString += ""
    }
    return jsonString
}

/*          USAGE          

var stringifiedJsonObject = jsonStringify(jsonObject) */