Question 130309 in Xcode Question posted in
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Xcode – Creating an an enum for segue identifiers

How would I go about extending an NSObject, NSStoryboardSegue.Identifier, to provide a set of cases as potential parameter types?

extension NSStoryboardSegue.Identifier {
  enum identifier: String {
    case showHelpWindow
  }
}    

extension ViewController {
      
  override func prepare(for segue: NSStoryboardSegue, sender: Any?) {
    if (segue.identifier == "showHelpWindow") {
      // What I have now
    }
    
    if segue.identifier == .showHelpWindow {
      // What I'm trying to get
    }
  }

  func showHelpWindow() {
    // What I have now
    performSegue(withIdentifier: "showHelpWindow", sender: self)
    // What I'm trying to get
    performSegue(withIdentifier: .showHelpWindow, sender: self)
  }
      
}
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2

Answers


  1. 0

    Define a protocol

    protocol SegueHandlerType {
    associatedtype SegueIdentifier : RawRepresentable
}

    and a protocol extension to overload performSegue. The segueIdentifer(for method is to get the identifier if there are multiple segues in the controller

    extension SegueHandlerType where Self : UIViewController, SegueIdentifier.RawValue == String {
    
    func performSegue(withIdentifier segueIdentifier : SegueIdentifier, sender: Any?) {
        performSegue(withIdentifier: segueIdentifier.rawValue, sender: sender)
    }
    
    func segueIdentifer(for segue : UIStoryboardSegue) -> SegueIdentifier {
        guard let identifier = segue.identifier, let segueIdentifier = SegueIdentifier(rawValue: identifier) else {
            fatalError("Invalid segue identifier (segue.identifier!)")
        }
        return segueIdentifier
    }
}

    To use it adopt the protocol in the view controller and declare an enum for the identifiers

    class ViewController: UIViewController, SegueHandlerType {

    enum SegueIdentifier : String {
        case showHelpWindow, showSomethingElse
    }

...

    func showHelpWindow() {

        performSegue(withIdentifier: .showHelpWindow, sender: self)
    }

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
          if case .showHelpWindow = segueIdentifer(for:segue) {


          }
    }
}
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  2. 0

    You don’t actually need to extend NSStoryboardSegue.Identifier at all. Just create your own enum:

    enum SegueIdentifier: String {
    case mySegue
}

    Add a custom == operator so that it can be compared with segue.identifier:

    static func ==(lhs: String?, rhs: SegueIdentifier) -> Bool {
    lhs == rhs.rawValue
}

    Then extend NSViewController to add an overload of performSegue that takes SegueIdentifier:

    extension NSViewController {
    func performSegue(withIdentifier identifier: SegueIdentifier, sender: Any?) {
        performSegue(withIdentifier: identifier.rawValue, sender: sender)
    }
}

    Usage:

    class MyViewController: NSViewController {
    override func prepare(for segue: NSStoryboardSegue, sender: Any?) {
        if segue.identifier == .mySegue {
            // ...
        }
    }
    
    func foo() {
        performSegue(withIdentifier: .mySegue, sender: nil)
    }
}
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