Connect to ViewController from AppDelegate (Swift)

Question

I have created a new OS X Cocoa Application using the standard Xcode Swift template (using StoryBoards).

I have implemented an IBAction in AppDelegate.swift to handle when the users selects "Open..." from the "File" menu. If the chosen file is a valid image file, I create an NSImage which I then want to display in the view of ViewController.

    @IBAction func openFile(sender: NSMenuItem) {
    var openPanel = NSOpenPanel()
    openPanel.beginWithCompletionHandler { (result :Int) -> Void in
        if result == NSFileHandlingPanelOKButton {
            if let imageURL = openPanel.URL {
                let image = NSImage(contentsOfURL: imageURL)
                // PRESENT image IN THE VIEW CONTROLLER
            }
        }
    }

However, I don't see any way to connect to ViewController from AppDelegate. I have only managed to find suggestions that I should look at self.window! in AppDelegate, but there is no such thing as a window in AppDelegate.

Thanks, Michael Knudsen

bluedome · Accepted Answer · 2014-12-17T16:05:39.680

18

It seems that AppDelegate can connect to objects only within Application Scene in a storyboard. If you want to get a ViewController, instantiate it from a storyboard.

sample:

@IBAction func menuAction(sender: AnyObject) {
    if let storyboard = NSStoryboard(name: "Main", bundle: nil) {
        let controller = storyboard.instantiateControllerWithIdentifier("VC1") as NSViewController

        if let window = NSApplication.sharedApplication().mainWindow {
            window.contentViewController = controller // just swap
        }
    }
}

edited Dec 17 '14 at 16:05

answered Dec 17 '14 at 14:30

bluedome

2,449
1
22
17

Once I have an instance, how would I use it? I tried just calling a function but that doesn't work (or rather, it expects arguments that I haven't defined in my method declaration). I assume there is some reason for this separation, but since Application Menu's can only call to the AppDelegate (and the menu is part of the UI) I don't understand why it is like this. Is there an easy way and/or a right way to let my Menu Item update my View? – Subcreation May 12 '15 at 18:38
1

how about using first responder? in a storyboard, connect menu's action to First Responder's action which you define as @IBAction. but `NSViewController` is not in responder chain, so set your controller to window's delegate(`NSWindow` is in responder chain). – bluedome May 13 '15 at 05:58

score 4 · Answer 2 · answered Nov 27 '16 at 15:55

4

You can access the mainWinow property and the contentViewController property to create a reference to your custom ViewController class. This is similar to the iOS rootViewController property.

let rootViewController = NSApplication.shared().mainWindow?.windowController?.contentViewController as! ViewController

Now you can use this reference to access IBOutlets on your main storyboard from your AppDelegate.

rootViewController.myTextView.textStorage?.mutableString.setString("Cats and dogs.")

This is good for a simple app with one Window with one ViewController.

answered Nov 27 '16 at 15:55

John Pavley

5,366
2
14
16

Excuse me, but accessing a reference to the root view controller from AppDelegate with NSApplication.shared() ? That doesn't sound right. – El Tomato Mar 14 '17 at 05:43
@ElTomato shared() may using parenthesis-free notation. eg) NSApplication.shared.mainWindow?.windowController?.contentViewController as! ViewController – Namo Oct 09 '20 at 09:53

score 1 · Answer 3 · edited May 23 '17 at 12:13

I was stuck trying to do this same thing recently and managed to get the event I needed to update my view by creating the @IBAction in my ViewController and control dragging to my Application's First Responder (above the menu in my storyboard view).

Here's the question that got me out of the woods: Application Menu Items Xcode

And thanks to Bluedome for the suggestion to connect it to First Responder's action.

score 0 · Answer 4 · answered Jan 25 '16 at 05:18

If you control-drag from the menu to the first responder (red cube above menu) and picked an existing action, then you can "responder chain" to your view controller. In my case I attached Open to openFile and then in my view controller I added the following

override var acceptsFirstResponder: Bool {
    return true
}

func openFile(sender: NSMenuItem) {
    print("In view controller")
}

and it worked without any changes in AppDelegate. Most of the menus are already hooked up to first responder so just add the matching function name in your view controller.

See this comment and this document on Event Handling Basics for more info.

score 0 · Answer 5 · answered Dec 15 '19 at 07:42

In Swift 5 and accessing new windows array:

@IBAction func menuAction(sender: AnyObject) {
    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    let controller = storyboard.instantiateInitialViewController()
    // The windows in the array are ordered from back to front by window level;
    // thus, the last window in the array is on top of all other app windows.
    // On app launch, UIApplication.shared.windows.count == 1 anyway.
    if let window = UIApplication.shared.windows.last {
        window.rootViewController = controller
    }
}

Connect to ViewController from AppDelegate (Swift)

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