如何在Swift中提供带有Error类型的本地化描述？我正在使用Swift 3语法定义自定义错误类型，我想提供一个用户友好的错误描述，该描述由对象的localizedDescription属性返回Error。我该怎么做？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.)"有没有办法让localizedDescription我返回我的自定义错误描述（“用户友好的错误描述。”）？请注意，此处的错误对象是类型Error而不是MyError。当然，我可以将对象强制转换为MyError(error as? MyError)?.localizedDescription但是有没有办法让它工作而不会转换为我的错误类型？
3 回答
繁华开满天机
TA贡献1816条经验 获得超4个赞
如Xcode 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协议提供本地化的错误描述。
在你的情况下：
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.customError
print(error.localizedDescription) // A user-friendly description of the error.
如果错误转换为NSError（始终可以），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.")
通过采用该CustomNSError协议，错误可以提供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贡献1802条经验 获得超4个赞
我还要补充一下，如果你的错误有这样的参数
enum NetworkError: LocalizedError {
case responseStatusError(status: Int, message: String)}您可以在本地化描述中调用这些参数，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"
}}你甚至可以这样缩短：
extension NetworkError {
public var errorDescription: String? {
switch self {
case let .responseStatusError(status, message):
return "Error with status \(status) and message \(message) was thrown"
}}
森栏
TA贡献1810条经验 获得超5个赞
使用结构可以是一种替代方案。静态本地化有点优雅：
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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