这样使用委托怎么样？本示例将更改按钮的标题。

@objc protocol SomeDelegate {
    func changeTitle(title: String)
}

class ViewController: NSViewController {

    weak var delegate: SomeDelegate?

    @IBAction func myAction(sender: AnyObject) {
        delegate?.changeTitle("NewTitle")
    }

}

class MainWindowController: NSWindowController, SomeDelegate {

    @IBOutlet weak var myButton: NSButton!

    override func windowDidLoad() {
        super.windowDidLoad()

        // Implement this method to handle any initialization after your window controller's window has been loaded from its nib file.
        let myVc = window!.contentViewController as! ViewController
        myVc.delegate = self

    }

    func changeTitle(title: String) {
        myButton.title = title
    }

}