swift的异常处理：本质是错误信息的传递方式

func response(from resultObject: Any) throws -> Response {

guard

let dict = resultObject as? [String: AnyObject],

let transaction = PendingTransaction.from(dict)

else {

throw CastError(actualValue: resultObject, expectedType: Response.self)

}

return transaction

}

func convertPrivateKeyToKeystoreFile(privateKey: String, passphrase: String) -> Result<[String: Any], KeystoreError> {

guard let data = Data(hexString: privateKey) else {

return .failure(KeystoreError.failedToImportPrivateKey)

}

do {

let key = try KeystoreKey(password: passphrase, key: data)

let data = try JSONEncoder().encode(key)

let dict = try JSONSerialization.jsonObject(with: data, options: []) as! [String: Any]

return .success(dict)

} catch {

return .failure(KeystoreError.failedToImportPrivateKey)

}

}

var asDictionary: [String: Any]? {

if let data = self.data(using: .utf8) {

do {

return try JSONSerialization.jsonObject(with: data, options: []) as? [String: Any]

} catch {

print(error.localizedDescription)

return [:]

}

}

return [:]

}