如果已经用下面的代码完成了它：

let addMyPopover = NSPopover()

if let popOverController = aViewController(xyz: data) {
            popOverController.closeDelegate = self
            addMyPopover.behavior = .Transient
            addMyPopover.contentViewController = popOverController
            addMyPopover.contentSize = CGSizeMake(450, 380)
            addMyPopover.showRelativeToRect(addButton.bounds,    ofView: addPhaseButton, preferredEdge: NSRectEdge.MinY)
        }

extension MyController: closeViewDelegate {
    func closePopover(sender: AnyObject?) {
       addMyPopover.performClose(sender)
    }
} 

protocol closeViewDelegate: class {
   func closePopover(sender: AnyObject?)
}

aViewController来自NSViewController类型

@IBAction func showPopover(_ sender: NSButton) {
    let vcPopover = NSStoryboard(name: "Main", bundle: nil).instantiateController(withIdentifier: "viewControllerPop") as! NSViewController
    self.presentViewController(vcPopover, asPopoverRelativeTo : sender.bounds, of : sender, preferredEdge: .maxY, behavior: .transient)
}