JolChr

enum Error: ErrorType {
    case SomeExpectedError
    case SomeUnexpectedError
}

func functionThatThrows() throws {
    throw Error.SomeExpectedError
}

XCTAssertThrowsError(try functionThatThrows(), "some message") { (error) in

JolChr

// disable error handling
try! division(numerator: 10, denominator: 5)

JolChr

enum DivisionError: Error {
  
  case dividedByZero
}

func division(numerator: Int, denominator: Int) throws {
  if denominator == 0 {
    throw DivisionError.dividedByZero
  }
    

JolChr

// create an enum with error values
enum DivisionError: Error {

  case dividedByZero
}

// create a throwing function using throws keyword
func division(numerator: Int, denominator: Int) throws {

  // throw error if divide by 0

JolChr

do {
  try division(numerator: 10, denominator: 0)
  ...
}

catch DivisionError.dividedByZero {
  // statement
}

JolChr

// call throwing function using try keyword
try division(numerator: 10, denominator: 0)

JolChr

// create throwing function using throws keyword
func division(numerator: Int, denominator: Int) throws {

// throw error if divide by 0
  if denominator == 0 {
    throw DivisionError.dividedByZero
  }
  ...
}

JolChr

class LoginViewController: UIViewController {
    
    @IBOutlet weak var nameTextField: UITextField!
    @IBOutlet weak var passwordTextField: UITextField!
    
    override func viewDidLoad() {
        
    }
    
    func showError(_ message: String) {

JolChr

extension ValidationError: LocalizedError {
    var errorDescription: String? {
        switch self {
        case .emptyName:
            return "Please enter name."
        case .shortName:
            return "Name is too short."
        case .longName:
            return "Name is too long."
        case .emptyPassword:

JolChr

func makeRequest() {
      do {
          let name = try ValidateService.validate(name: nameTextField.text)
          let password = try ValidateService.validate(password: passwordTextField.text)
          self.sendLoginRequest(name: name, password: password)
      } catch {
          self.showAlert(error.localizedDescription)
      }
  }