swift 自定义类型的 Log 输出格式

Java 中想自定义 Log 中的类的输出格式，override toString 方法即可 而 Swift 中需要继承特定的协议 CustomStringConvertible

例如

extension DataResponse: CustomStringConvertible, CustomDebugStringConvertible {
    /// The textual representation used when written to an output stream, which includes whether the result was a
    /// success or failure.
    public var description: String {
        return result.debugDescription
    }

    /// The debug textual representation used when written to an output stream, which includes the URL request, the URL
    /// response, the server data, the response serialization result and the timeline.
    public var debugDescription: String {
        let requestDescription = request.map { "\($0.httpMethod ?? "GET") \($0)"} ?? "nil"
        let requestBody = request?.httpBody.map { String(decoding: $0, as: UTF8.self) } ?? "None"
        let responseDescription = response.map { "\($0)" } ?? "nil"
        let responseBody = data.map { String(decoding: $0, as: UTF8.self) } ?? "None"

        return """
        [Request]: \(requestDescription)
        [Request Body]: \n\(requestBody)
        [Response]: \(responseDescription)
        [Response Body]: \n\(responseBody)
        [Result]: \(result)
        [Timeline]: \(timeline.debugDescription)
        """
    }
}