如何在Swift中提供帶有Error類型的本地化描述？我正在使用Swift 3語法定義自定義錯誤類型，我想提供一個用戶友好的錯誤描述，該描述由對象的localizedDescription屬性返回Error。我該怎么做？public enum MyError: Error {
case customError var localizedDescription: String {
switch self {
case .customError:
return NSLocalizedString("A user-friendly description of the error.", comment: "My error")
}
}}let error: Error = MyError.customError
error.localizedDescription// "The operation couldn’t be completed. (MyError error 0.)"有沒有辦法讓localizedDescription我返回我的自定義錯誤描述（“用戶友好的錯誤描述。”）？請注意，此處的錯誤對象是類型Error而不是MyError。當然，我可以將對象強制轉(zhuǎn)換為MyError(error as? MyError)?.localizedDescription但是有沒有辦法讓它工作而不會轉(zhuǎn)換為我的錯誤類型？
3 回答
繁華開滿天機
TA貢獻1816條經(jīng)驗 獲得超4個贊
如Xcode 8 beta 6發(fā)行說明中所述，
Swift定義的錯誤類型可以通過采用新的LocalizedError協(xié)議提供本地化的錯誤描述。
在你的情況下：
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.customError
print(error.localizedDescription) // A user-friendly description of the error.
如果錯誤轉(zhuǎn)換為NSError（始終可以），您可以提供更多信息：
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 NSError
print(error.localizedDescription) // I failed.
print(error.localizedFailureReason) // Optional("I don\'t know why.")
print(error.localizedRecoverySuggestion) // Optional("Switch it off and on again.")
通過采用該CustomNSError協(xié)議，錯誤可以提供userInfo字典（以及a domain和code）。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 NSError
if let line = error.userInfo["line"] as? Int {
print("Error in line", line) // Error in line 13
}
print(error.code) // 999
print(error.domain) // myDomain
慕虎7371278
TA貢獻1802條經(jīng)驗 獲得超4個贊
我還要補充一下，如果你的錯誤有這樣的參數(shù)
enum NetworkError: LocalizedError {
case responseStatusError(status: Int, message: String)}您可以在本地化描述中調(diào)用這些參數(shù)，如下所示：
extension NetworkError {
public var errorDescription: String? {
switch self {
case .responseStatusError(status: let status, message: let message):
return "Error with status \(status) and message \(message) was thrown"
}}你甚至可以這樣縮短：
extension NetworkError {
public var errorDescription: String? {
switch self {
case let .responseStatusError(status, message):
return "Error with status \(status) and message \(message) was thrown"
}}
森欄
TA貢獻1810條經(jīng)驗 獲得超5個贊
使用結(jié)構(gòu)可以是一種替代方案。靜態(tài)本地化有點優(yōu)雅：
import Foundationstruct MyError: LocalizedError, Equatable {
private var description: String!
init(description: String) {
self.description = description }
var errorDescription: String? {
return description }
public static func ==(lhs: MyError, rhs: MyError) -> Bool {
return lhs.description == rhs.description }}extension MyError {
static let noConnection = MyError(description: NSLocalizedString("No internet connection",comment: ""))
static let requestFailed = MyError(description: NSLocalizedString("Request failed",comment: ""))}func throwNoConnectionError() throws {
throw MyError.noConnection}do {
try throwNoConnectionError()}catch let myError as MyError {
switch myError {
case .noConnection:
print("noConnection: \(myError.localizedDescription)")
case .requestFailed:
print("requestFailed: \(myError.localizedDescription)")
default:
print("default: \(myError.localizedDescription)")
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