swift JSONString和字典互转

extension Dictionary {
    public func toJSONString() -> String? {
        guard let data = try? JSONSerialization.data(withJSONObject: self, options: []) else {
            return nil
        }
        guard let string = String(data: data, encoding: .utf8) else {
            return nil
        }
        return string
    }
}

extension String {
    public func toDictionary() -> [String : Any] {
        var result = [String : Any]()
        guard !self.isEmpty else { return result }
        guard let dataSelf = self.data(using: .utf8) else {
            return result
        }
        if let dic = try? JSONSerialization.jsonObject(with: dataSelf,
                           options: .mutableContainers) as? [String : Any] {
            result = dic
        }
        return result
    }
}