Swift has Error protocol that does not have anything default. iOS developers have to extend this protocol to deal with errors in their app. I will introduce a very simple example to manage custom errors. You can define your error cases like following.
// Error+Extension.swift
enum CustomError: Error {
case errorOne
case errorTwo
case errorThree(message: String)
}
extension CustomError: LocalizedError {
var errorDescription: String? {
switch self {
case .errorOne:
return NSLocalizedString("Error one's description", comment: "Custom Error")
case .errorTwo:
return NSLocalizedString("Error two's description", comment: "Custom Error")
case .errorThree(let message):
return NSLocalizedString(message, comment: "Custom Error")
}
}
}
I wrote an article about handling UIAlertController. Using this AlertController, Error+Extension.swift can be improved like this.
// Error+Extension.swift
enum CustomError: Error {
case errorOne
case errorTwo
case errorThree(message: String)
}
extension CustomError: LocalizedError {
var errorDescription: String? {
switch self {
case .errorOne:
return NSLocalizedString("Error one's description", comment: "Custom Error")
case .errorTwo:
return NSLocalizedString("Error two's description", comment: "Custom Error")
case .errorThree(let message):
return NSLocalizedString(message, comment: "Custom Error")
}
}
}
extension Error {
func displayAlert(completion: (() -> Void)? = nil) {
let alert = AlertController(title: "Error", message: localizedDescription, preferredStyle: .alert)
let action = UIAlertAction(title: "OK", style: .default)
alert.addAction(action)
alert.show(completion: completion)
}
}
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