Error as NSError

Error_as_NSError.swift

import Foundation

struct StructError: Error {
    var localizedDescription: String { "StructError.localizedDescription" }
}

class ClassError: Error {
    var localizedDescription: String { "ClassError.localizedDescription" }
}

enum EnumError: Error {
    case case1
    case case2
    case case3

    var localizedDescription: String { "EnumError.localizedDescription" }
}

enum IntEnumError: String, Error {
    case case1
    case case2
    case case3

    var localizedDescription: String { "IntEnumError.localizedDescription" }
}

enum StringEnumError: String, Error {
    case case1
    case case2
    case case3

    var localizedDescription: String { "StringEnumError.localizedDescription" }
}

struct StructLocalizedError: LocalizedError {
    var errorDescription: String? { "StructLocalizedError.errorDescription" }
    var failureReason: String? { "StructLocalizedError.failureReason" }
    var recoverySuggestion: String? { "StructLocalizedError.recoverySuggestion" }
    var helpAnchor: String? { "StructLocalizedError.helpAnchor" }
}

struct StructRecoverableError: RecoverableError {
    var recoveryOptions: [String] { ["StructRecoverableError.recoveryOptions.1", "StructRecoverableError.recoveryOptions.2"] }

    func attemptRecovery(optionIndex recoveryOptionIndex: Int, resultHandler handler: @escaping (Bool) -> Void) {
        handler(true)
    }

    func attemptRecovery(optionIndex recoveryOptionIndex: Int) -> Bool {
        return true
    }
}

struct StructCustomNSError: CustomNSError {
    static var errorDomain: String { "StructCustomNSError.errorDomain" }
    var errorCode: Int { 123 }
    var errorUserInfo: [String : Any] { ["StructCustomNSError.UserInfo.Key1": 456, "StructCustomNSError.UserInfo.Key2": 789] }
}

func printErrorAsNSError(_ error: Error) {
    print("")
    print(String(describing: type(of: error)))
    let nsError = error as NSError
    print("domain                     ", nsError.domain)
    print("code                       ", nsError.code)
    print("userInfo                   ", nsError.userInfo)
    print("localizedDescription       ", nsError.localizedDescription)
    print("localizedFailureReason     ", nsError.localizedFailureReason ?? "(nil)")
    print("localizedRecoverySuggestion", nsError.localizedRecoverySuggestion ?? "(nil)")
    print("localizedRecoveryOptions   ", nsError.localizedRecoveryOptions ?? "(nil)")
    print("recoveryAttempter          ", nsError.recoveryAttempter ?? "(nil)")
    print("helpAnchor                 ", nsError.helpAnchor ?? "(nil)")
}

printErrorAsNSError(StructError())
printErrorAsNSError(ClassError())
printErrorAsNSError(EnumError.case3)
printErrorAsNSError(StringEnumError.case3)
printErrorAsNSError(IntEnumError.case3)
printErrorAsNSError(StructLocalizedError())
printErrorAsNSError(StructRecoverableError())
printErrorAsNSError(StructCustomNSError())

Result

StructError
domain                      __lldb_expr_7.StructError
code                        1
userInfo                    [:]
localizedDescription        The operation couldn’t be completed. (__lldb_expr_7.StructError error 1.)
localizedFailureReason      (nil)
localizedRecoverySuggestion (nil)
localizedRecoveryOptions    (nil)
recoveryAttempter           (nil)
helpAnchor                  (nil)

ClassError
domain                      __lldb_expr_7.ClassError
code                        1
userInfo                    [:]
localizedDescription        The operation couldn’t be completed. (__lldb_expr_7.ClassError error 1.)
localizedFailureReason      (nil)
localizedRecoverySuggestion (nil)
localizedRecoveryOptions    (nil)
recoveryAttempter           (nil)
helpAnchor                  (nil)

EnumError
domain                      __lldb_expr_7.EnumError
code                        2
userInfo                    [:]
localizedDescription        The operation couldn’t be completed. (__lldb_expr_7.EnumError error 2.)
localizedFailureReason      (nil)
localizedRecoverySuggestion (nil)
localizedRecoveryOptions    (nil)
recoveryAttempter           (nil)
helpAnchor                  (nil)

StringEnumError
domain                      __lldb_expr_7.StringEnumError
code                        2
userInfo                    [:]
localizedDescription        The operation couldn’t be completed. (__lldb_expr_7.StringEnumError error 2.)
localizedFailureReason      (nil)
localizedRecoverySuggestion (nil)
localizedRecoveryOptions    (nil)
recoveryAttempter           (nil)
helpAnchor                  (nil)

IntEnumError
domain                      __lldb_expr_7.IntEnumError
code                        2
userInfo                    [:]
localizedDescription        The operation couldn’t be completed. (__lldb_expr_7.IntEnumError error 2.)
localizedFailureReason      (nil)
localizedRecoverySuggestion (nil)
localizedRecoveryOptions    (nil)
recoveryAttempter           (nil)
helpAnchor                  (nil)

StructLocalizedError
domain                      __lldb_expr_7.StructLocalizedError
code                        1
userInfo                    [:]
localizedDescription        StructLocalizedError.errorDescription
localizedFailureReason      StructLocalizedError.failureReason
localizedRecoverySuggestion StructLocalizedError.recoverySuggestion
localizedRecoveryOptions    (nil)
recoveryAttempter           (nil)
helpAnchor                  StructLocalizedError.helpAnchor

StructRecoverableError
domain                      __lldb_expr_7.StructRecoverableError
code                        1
userInfo                    [:]
localizedDescription        The operation couldn’t be completed. (__lldb_expr_7.StructRecoverableError error 1.)
localizedFailureReason      (nil)
localizedRecoverySuggestion (nil)
localizedRecoveryOptions    ["StructRecoverableError.recoveryOptions.1", "StructRecoverableError.recoveryOptions.2"]
recoveryAttempter           Foundation.__NSErrorRecoveryAttempter
helpAnchor                  (nil)

StructCustomNSError
domain                      StructCustomNSError.errorDomain
code                        123
userInfo                    ["StructCustomNSError.UserInfo.Key2": 789, "StructCustomNSError.UserInfo.Key1": 456]
localizedDescription        The operation couldn’t be completed. (StructCustomNSError.errorDomain error 123.)
localizedFailureReason      (nil)
localizedRecoverySuggestion (nil)
localizedRecoveryOptions    (nil)
recoveryAttempter           (nil)
helpAnchor                  (nil)