Swift - return String from enum Error

Question

How can I return only a string from an error?

I would like to return only: "not found" or "can't delete".

Right now, the returned error is: The operation couldn't be completed. (Invoice.BackEnd Error 2.)

code that makes the request:

enum BackendError: Error {
    case urlError(reason: String)
    case objectSerialization(reason: String)
    case objectDeletion(reason: String)
}

struct Meta: Codable {
  let sucess: String
  let message: String!
}


        if let httpResponse = response as? HTTPURLResponse{
            if httpResponse.statusCode == 200{
                print("deleted")
                let response = Meta(sucess: "yes", message: "deleted")
                completionHandler(response, nil)
                return
            }
            else if (httpResponse.statusCode == 404) {
                let error = BackendError.objectDeletion(reason: "not found")
                completionHandler(nil, error)
                return
            }
            else {
                let error = BackendError.objectDeletion(reason: "can't delete")
                completionHandler(nil, error)
                return
            }
        }

part of the code inside the delete button:

makeDelete(httpMethod: "DELETE",endpoint: endPoint,
                parameters: [:],
        completionHandler: { (container : Meta?, error : Error?) in
            if let error = error {
                print("error on /delete")                 
                self.showAlert(title: "Error", message: error.localizedDescription)
                return
            }
            self.wasDeleted = true

            //change message and use the custom func like on error.
            let alert = UIAlertController(title: "Success!", message: "Client Deleted.", preferredStyle: .alert)
            let OKAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler: {
                (_)in
                self.performSegue(withIdentifier: "unwindToClients", sender: self)
            })
            alert.addAction(OKAction)

            DispatchQueue.main.async(execute: {
                self.present(alert, animated: true, completion: nil)
            })

    } )

Answer 1

Start by defining your completion handler to return BackendError instead of Error. That will make things a little easier.

Then you need to use a switch on the error to get the reason value:

makeDelete(httpMethod: "DELETE",endpoint: endPoint,
            parameters: [:],
    completionHandler: { (container : Meta?, error : BackendError?) in
        if let error = error {
            print("error on /delete")  
            let message: String
            switch error {
                case let .objectDeletion(reason):
                    message = reason
                default:
                    message = error.localizeDescription
            }
            self.showAlert(title: "Error", message: message)
            return
        }