OS X Cocoa Swift: Setting up a ViewController programmatically (without Storyboard or nib files)

Question

I am currently trying to rebuild an existing project in a purely programmatic way (without storyboard and nib files). I know that there are already some posts about that, but they didn't really helped me. This is a way to solve it:

main.swift

import Cocoa

let delegate = AppDelegate()
NS Application.shared().delegate = delegate

let ret = NSApplicationMain(CommandLine.argc, CommandLine.unsafeArgv)`

AppDelegate.swift

import Cocoa

class AppDelegate: NSObject, NSApplicationDelegate {

   let viewController = ViewController()
   let window = NSWindow(contentRect: NSMakeRect(0, 0, NSScreen.main()!.frame.size.width, NSScreen.main()!.frame.size.height), styleMask: [.titled, .closable, .miniaturizable, .resizable], backing: NSBackingStoreType.buffered, defer: false)

   func applicationDidFinishLaunching(_ aNotification: Notification) {
       viewController.view = NSView(NSMakeRect(0, 0, window.frame.size.width, window.frame.size.height))
       viewController.view.wantsLayer = true
       window.contentView!.addSubview(viewController.view)
       window.makeKeyAndOrderFront(nil)
   }

}

ViewController.swift

import Cocoa

class ViewController: NSViewController {

    override func viewDidAppear() {
        let button = NSButton(frame: NSRect(x: 150, y: 200, width: 300, height: 30))
        button.action = #selector(ViewController.buttonPressed(_:))
        button.target = self
        view.addSubview(button)
    }

    func buttonPressed(_: Any?) {
        print("OK")
    }

}

Later, the plan is to switch with these buttons between different View Controllers and show different Views. Is this the right way at all or is there a "better" way to do this? My goal is to have one window and different ViewControllers. Thank you for your help

Answer 1

You also need to set the target on the button. The action tells it which method to call, but without a target it has nothing to call the method on.

You may also need to change your action method to allow for the sender parameter: func buttonPressed(_: Any?) {...} and set the action to #selector(ViewController.buttonPressed(_:)).

I also just noticed that your view controller is only being held in a local variable in applicationDidFinishLaunching. It should be a property of the AppDelegate so that there is a reference to it, otherwise it will get deleted right away.