enum_protocols.swift

enum EmailValidationError: Error {
    // TODO: - Cases
    case empty
    // TODO: - Cases can be declared on a single line
    case noDomain(String)
    case invalid(String)
}

extension EmailValidationError: LocalizedError {
    
    var errorDescription: String? {
        switch self {
        case .invalid:
            return "This email is incorrect. Please, try again"
        case .empty:
            return "This email is empty. Please, fill it"
        case .noDomain:
            return "This email without domain. Please, try again"
        }
    }
    
}

let error = EmailValidationError.empty
print("error: \(error.localizedDescription)")