为什么UIDocumentMenu代表自己不工作？

Question

我正在关注UIDocumentMenuViewController的Apple文档，以下是我的代码。 importMenu.delegate = self不起作用，Xcode显示：无法分配类型的值＆＃39; ViewController＆＃39;键入＆＃39; UIDocumentMenuDelegate？＆＃39; 。请帮忙。谢谢！

import UIKit

class ViewController: UIViewController  {

override func viewDidLoad() {
    super.viewDidLoad()

    let importMenu = UIDocumentMenuViewController(documentTypes: ["public.text", "public.data"], inMode: .Import)

    importMenu.delegate = self

    self.presentViewController(importMenu, animated: true, completion: nil)

   }
}

Answer 1

根据UIDocumentMenuDelegate Protocol Reference，您的ViewController必须符合UIDocumentMenuDelegate并且必须实施documentMenu:didPickDocumentPicker:

extension ViewController: UIDocumentMenuDelegate {
    func documentMenu(documentMenu: UIDocumentMenuViewController, didPickDocumentPicker documentPicker: UIDocumentPickerViewController) {
        // do stuffs here
    }
}

Answer 2

您的委托类应该从视图控制器中的UIDocumentMenuViewDelegate扩展

import UIKit

class ViewController: UIViewController, UIDocumentMenuViewDelegate  {

override func viewDidLoad() {
    super.viewDidLoad()

    let importMenu = UIDocumentMenuViewController(documentTypes: ["public.text", "public.data"], inMode: .Import)

    importMenu.delegate = self

    self.presentViewController(importMenu, animated: true, completion: nil)

   }
}