how can i cast server error message to AFError - ios

Question

i am unable to find some way to cast custom message to AFError
class APIClient {
#discardableResult
static func performRequest<T:Decodable>(route:APIRouter, decoder: JSONDecoder = JSONDecoder(), completion:#escaping (Result<T, AFError>)->Void) -> DataRequest {
return AF.request(route).validate(statusCode: 200..<300).responseDecodable(decoder: decoder) { (response: DataResponse<T, AFError>) in
switch response.result {
case .success(let value):
completion(.success(value))
case .failure(let error):
let err = MYError(description: "here goes some custom error message")
let customErr = err .asAFError
completion(.failure(customErr!))
}
}
}
and my custom error message struct
struct MYError : Error{
let description : String
var localizedDescription: String {
return NSLocalizedString(description, comment: "")
}

Answer 1

Do you know what AFError you want to cast your error to? That's the first step to your answer because the AFError is a type of error class not one specific error. Here's my approach.
First I would change the error to an enum Errors defined as an Error just like the Struct you had. Then add your custom error as a case. Define your description and specify there what you would like the error message to be for each case (specific error).
Second, define what your Error should correspond to in an AFError for each case. This way you can specify and pass the data that will be required for some of the AFErrors like the example of SomeOtherError.
enum Errors: Error {
var localizedDescription: String {
var str: String = ""
switch self {
case .MyError: str = "Some custom error message"
case .SomeOtherError: str = "This would be another error and message"
}
return NSLocalizedString(str, comment: "")
}
var asAFError: AFError? {
switch self {
case .MyError: return .explicitlyCancelled
case .SomeOtherError(let data): return .sessionDeinitialized(data)
default: return nil
}
}
case MyError
case SomeOtherError(Data)
}
Lastly use a guard statement incase you throw and error that cannot be defined as an AFError, then pass that error to your completion like normal.
class APIClient {
#discardableResult
static func performRequest<T:Decodable>(route: APIRouter, decoder: JSONDecoder = JSONDecoder(), completion:#escaping (Result<T, AFError>)->Void) -> DataRequest {
return AF.request(route).validate(statusCode: 200..<300).responseDecodable(decoder: decoder) { (response: DataResponse<T, AFError>) in
switch response.result {
case .success(let value):
completion(.success(value))
case .failure(let error):
guard let err = Errors.MyError.asAFError
else { return error }
completion(.failure(err))
}
}
}
}