如何从Alamofire错误中获得底层错误？

Question

对于这种请求：

Alamofire.request("https://google.com").responseCollection { (response: DataResponse<[User]>) in 
    guard response.result.isSuccess else { 
    print(response.error) 

    return 
    } 
} 

我看到该印刷在控制台：

可选（my_app_name.BackendError.jsonSerialization（Alamofire.AFError.responseSerializationFailed（Alamofire.AFError.ResponseSerializationFailureReason .jsonSerializationFailed（错误 域= NSCocoaErrorDomain代码= 3840“字符周围的值无效 0.”UserInfo = {NSDebugDescription =字符0周围的值无效}））） ）

我已经试过：

Alamofire.request("https://google.com").responseCollection { (response: DataResponse<[User]>) in 
    guard response.result.isSuccess else { 
    print(response.error) 

    if let error1 = response.error as? AFError { 
     print(error1) // Execution DOES NOT reach here. 
    } 

    if let error2 = response.error as? BackendError { 
     print(error2) // Execution DOES reach here. 
    } 

    return 
    } 
} 

print(error2)上面打印：

jsonSerialization（Alamofire.AFError.responseSerializationFailed（Alamofire.AFError.ResponseSerializationFailureReason.jsonSerializationFailed（错误 Domain = NSCocoaErrorDomain Code = 3840“字符周围的值无效 0.”UserInfo = {NSDebugDescr在字符0 iption =无效值}）））

我想要做的就是在底层的错误，所以我可以解析domain，code和userInfo性能。

我创建BackendError枚举该Alamofire提供作为一个例子在https://github.com/Alamofire/Alamofire#handling-errors：

enum BackendError: Error { 
    case network(error: Error) // Capture any underlying Error from the URLSession API 
    case dataSerialization(error: Error) 
    case jsonSerialization(error: Error) 
    case xmlSerialization(error: Error) 
    case objectSerialization(reason: String) 
} 

和我还实施了例如通用响应对象序列完全一样，例如在https://github.com/Alamofire/Alamofire#generic-response-object-serialization：

extension DataRequest { 
    @discardableResult 
    func responseCollection<T: ResponseCollectionSerializable>(
    queue: DispatchQueue? = nil, 
    completionHandler: @escaping (DataResponse<[T]>) -> Void) -> Self { 
    let responseSerializer = DataResponseSerializer<[T]> { request, response, data, error in 
     guard error == nil else { 
     return .failure(BackendError.network(error: error!)) 
     } 

     let jsonSerializer = DataRequest.jsonResponseSerializer(options: .allowFragments) 
     let result = jsonSerializer.serializeResponse(request, response, data, nil) 

     guard case let .success(jsonObject) = result else { 
     return .failure(BackendError.jsonSerialization(error: result.error!)) 
     } 

     guard let response = response else { 
     let reason = "Response collection could not be serialized due to nil response." 
     return .failure(BackendError.objectSerialization(reason: reason)) 
     } 

     return .success(T.collection(from: response, withRepresentation: jsonObject)) 
    } 

    return response(responseSerializer: responseSerializer, completionHandler: completionHandler) 
    } 
} 

我认为有switch es，case s，并且从BackendError,AFError，Error，和/或NSError，但我似乎无法得到它。

如何获取底层错误，以便我可以解析domain,code和userInfo属性？

我使用的是Swift 3和Alamofire 4.3.0。

Answer 1

看response.result：

if case let .failure(error) = response.result { 
    let error = error as NSError 
    print("\(error.domain)") 
    print("\(error.code)") 
    print("\(error.userInfo)") 
}