Swift: programmatically enumerate outgoing segues from a UIVIewController

问题

I want to list the outgoing segues from a UIViewController, as described in Programmatically enumerate outgoing Segues for a UIViewController, but in Swift. (Swift 2, Xcode 7, iOS8+).

I can do

override func viewDidLoad() {
    super.viewDidLoad()
    let s = valueForKey("storyboardSegueTemplates")
    print("switchingVC: segues: \(s)") 
}

and that produces output like

switchingVC: segues: Optional((
    "<UIStoryboardPresentationSegueTemplate: 0x1754a130>",
    "<UIStoryboardPresentationSegueTemplate: 0x17534f60>",
    "<UIStoryboardPresentationSegueTemplate: 0x17534fc0>"
))

but I struggle to produce anything after that. I can't find any definition of the UIStoryboardPresentationSegueTemplate. How can I persuade Swift to tell me what's inside it? How can I find the segue identifier?

Thanks!

回答1:

this valueForKey("storyboardSegueTemplates") is UNDOCUMENTED property and UIStoryboardPresentationSegueTemplate is UNDOCUMENTED class. Beware of rejection from App Store if you are uploading application to App Store.

If you want to use this in your in-house projects, use as following

for template in (valueForKey("storyboardSegueTemplates") as? [AnyObject])! {
    if let identifier = template.valueForKey("identifier") as? String {
        print("identifier - " + identifier)
    }
    else {
        print("no identifier for \(template)")
    }
}

Found from https://github.com/JaviSoto/iOS9-Runtime-Headers/blob/master/Frameworks/UIKit.framework/UIStoryboardSegueTemplate.h

回答2:

As per Swift 4.2 and from https://stackoverflow.com/a/35060917/1058199. Thanks /johnykutty.

import UIKit

extension UIViewController {

     // Segue aids in Swift
     @objc func isValidSegue(_ segueId: String?) -> Bool {
        let filteredArray = (value(forKey: "storyboardSegueTemplates") as? NSArray)?.filtered(using: NSPredicate(format: "identifier = %@", segueId ?? ""))
        let isValid = (filteredArray?.count ?? 0) > 0
        return isValid
     }

     @objc func segues() -> Array<Any>? {
        let segues = self.value(forKey: "storyboardSegueTemplates")
        return segues as! Array<Any>?
     }

    @objc func segueNames() -> Array<AnyHashable> {
        var segueNames = Array<Any>()

        let filteredArray = (value(forKey: "storyboardSegueTemplates") as? NSArray)?.filtered(using: NSPredicate(format: "identifier != nil" ))

        for template in filteredArray! as [AnyObject] {
           if let identifier = (template.value(forKey: "identifier") as? String) {
               segueNames.append(identifier)
            }
            else {
                segueNames.append("no identifier for \(template)")
            }
        }

        return segueNames as! Array<AnyHashable>
    }
}

I know my use of predicates could be better, but Swift is such a PITA when dealing with iterating arrays. Please feel free to improve this.

来源：https://stackoverflow.com/questions/35060206/swift-programmatically-enumerate-outgoing-segues-from-a-uiviewcontroller

标签

swift

uistoryboardsegue