#selector 的参数不引用“@objc”方法、属性或初始化程序答案

【问题标题】：Argument of #selector does not refer to an '@objc' method, property or initializer#selector 的参数不引用“@objc”方法、属性或初始化程序
【发布时间】：2019-03-13 23:45:54
【问题描述】：

以下是我的代码，我正在关注在线教程，但出现上述错误。

import UIKit
import MultipeerConnectivity

class ViewController: UIViewController, MCBrowserViewControllerDelegate {



    @IBOutlet var xField: [MyImageView]!

    var appDelegate:AppDelegate!

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        appDelegate = UIApplication.shared.delegate as? AppDelegate
        appDelegate.mpcHandling.gettingPeerConnection(displayName: UIDevice.current.name)
        appDelegate.mpcHandling.gettingSession()
        appDelegate.mpcHandling.showingSelf(show: true)

        //handling peer state notification

        //getting error for the below mentioned line

        NotificationCenter.default.addObserver(self, selector: #selector("peerChangedNotification:"), name: NSNotification.Name(rawValue: "MPC_DidChangeStateNotification"), object: nil)

        NotificationCenter.default.addObserver(self, selector: Selector("handleReceivedNotification:"), name: NSNotification.Name(rawValue: "MPC_DidReceiveNotification"), object: nil)

        mainLogicField()

    }

    @objc func peerChangedNotification(notification:NSNotification){
        let userInfo = NSDictionary(dictionary: notification.userInfo!)

        let state = userInfo.object(forKey: "state") as! Int

        if state != MCSessionState.connecting.rawValue{
            //Now we inform user that we have connected
            self.navigationItem.title = "Connected Successfully"
        }
    }


    @IBAction func getConnected(_ sender: Any) {

        if appDelegate.mpcHandling.gameSession != nil {
            appDelegate.mpcHandling.gettingBrowser()
            appDelegate.mpcHandling.browser.delegate = self

            self.present(appDelegate.mpcHandling.browser, animated: true, completion: nil
            )

        }

    }




    func mainLogicField() {
        for index in 0 ... xField.count - 1 {

            let recognizeGestureTouch = UITapGestureRecognizer(target: self, action: "fieldTapped")

            recognizeGestureTouch.numberOfTapsRequired = 1

            xField[index].addGestureRecognizer(recognizeGestureTouch)
        }
    }

    func browserViewControllerDidFinish(_ browserViewController: MCBrowserViewController) {
        appDelegate.mpcHandling.browser.dismiss(animated: true, completion: nil)
    }

    func browserViewControllerWasCancelled(_ browserViewController: MCBrowserViewController) {
        appDelegate.mpcHandling.browser.dismiss(animated: true, completion: nil)
    }

}

不知道出了什么问题，因为我也使用了#selector 和@objc 作为我的函数。网上教程刚刚用到了 NotificationCenter.default.addObserver(self, selector: "peerChangedNotification:", name: NSNotification.Name(rawValue: "MPC_DidChangeStateNotification"), object: nil) 没有添加#selector，但如果我删除#selector，它会给我一个警告，指出“没有使用Objective-C选择器'peerChangedNotification'声明的方法”。我正在尝试使用 mutipeer 连接 2 台设备

【问题讨论】：

您使用的选择器语法错误。
提示：#selector 不带字符串。

标签： swift4 xcode10

【解决方案1】：

Selector() : 它接收字符串/字符串文字作为参数。以前用过，#selector是升级定义。

#selector : 您试图在#selector 中传递一个字符串，而它需要Objective-C 类型的函数引用。正确的例子是：

NotificationCenter.default.addObserver(self, selector: #selector(peerChangedNotification(notification:)), name: NSNotification.Name("MPC_DidChangeStateNotification"), object: nil)

【讨论】：