如Xpre 8 beta 6发行说明中所述，
Swift定义的错误类型可以通过采用新的LocalizedError协议来提供本地化的错误描述。
在您的情况下：
public enum MyError: Error { case customError}extension MyError: LocalizedError { public var errorDescription: String? { switch self { case .customError: return NSLocalizedString("A user-friendly description of the error.", comment: "My error") } }}let error: Error = MyError.customErrorprint(error.localizedDescription) // A user-friendly description of the error.如果将错误转换为错误，则可以提供更多信息
NSError（总是可能的）：
extension MyError : LocalizedError { public var errorDescription: String? { switch self { case .customError: return NSLocalizedString("I failed.", comment: "") } } public var failureReason: String? { switch self { case .customError: return NSLocalizedString("I don't know why.", comment: "") } } public var recoverySuggestion: String? { switch self { case .customError: return NSLocalizedString("Switch it off and on again.", comment: "") } }}let error = MyError.customError as NSErrorprint(error.localizedDescription) // I failed.print(error.localizedFailureReason) // Optional("I don't know why.")print(error.localizedRecoverySuggestion) // Optional("Switch it off and on again.")通过采用该
CustomNSError协议，错误可以提供
userInfo字典（以及a
domain和
pre）。例：
extension MyError: CustomNSError { public static var errorDomain: String { return "myDomain" } public var errorCode: Int { switch self { case .customError: return 999 } } public var errorUserInfo: [String : Any] { switch self { case .customError: return [ "line": 13] } }}let error = MyError.customError as NSErrorif let line = error.userInfo["line"] as? Int { print("Error in line", line) // Error in line 13}print(error.pre) // 999print(error.domain) // myDomain
