https://www.cnblogs.com/yajunLi/p/6549859.html

直接上程式碼吧

1、JSONString轉換為字典

 /// JSONString轉換為字典
    ///
    /// - Parameter jsonString: <#jsonString description#>
    /// - Returns: <#return value description#>
    func getDictionaryFromJSONString(jsonString:String) ->NSDictionary{

        let jsonData:Data 
 
= jsonString.data(using: .utf8)!

        let dict = try? JSONSerialization.jsonObject(with: jsonData, options: .mutableContainers)
        if dict != nil {
            return dict as! NSDictionary
        }
        return NSDictionary()
        

    }

2、字典轉換為JSONString

    /**
     字典轉換為JSONString
     
     - parameter dictionary: 字典引數
     
     - returns: JSONString
     
 
*/
    func getJSONStringFromDictionary(dictionary:NSDictionary) -> String {
        if (!JSONSerialization.isValidJSONObject(dictionary)) {
            print("無法解析出JSONString")
            return ""
        }
        let data : NSData! = try? JSONSerialization.data(withJSONObject: dictionary, options: []) as
 
 NSData!
        let JSONString = NSString(data:data as Data,encoding: String.Encoding.utf8.rawValue)
        return JSONString! as String

    }