Question

我将要编写一个具有多个游戏模式的小型应用程序。现在，我希望主类的模式（其中用滑块设置游戏模式）在不同的类中显示为标签。我收到错误消息：线程1：致命错误：意外地发现nil，同时隐式展开了一个可选值。

我有几个ViewController。首先，我有滑块。在第二个按钮上，我有两个按钮可以决定是真还是敢。在第三个标签上，我有应该更改的标签。在第一个ViewController上，有一个“开始”按钮，它将启动游戏。

我已经尝试将委托放入viewDidLoad函数中，但是没有用。

我的Slider在主类“ ViewController”中。 choiceButtonTapped在类“ ThisViewController”中。游戏模式应该显示在“ ThisViewController”中，并使用“ ViewController”类中的滑块进行设置。

以下是我的代码的一部分：

我的代表：

protocol SpielmodusDelegate {
  func didChooseGamemode(gm: String)
}

我的滑块：

var selectionDelegate: SpielmodusDelegate!

@IBAction gamemodeSliderChanges(_ sender: UISlider) {
  if (currentValue > 0.8 && currentvalue < 1) {
    gamemodeLabel.text = dataSource[4]
    selectionDelegate.didChooseGamemode(gm: "Extrem") <-------ERROR
  }
}

我要在其中导入游戏模式的其他班级：

@IBAction func chooseButtonTapped(_ sender: UIButton) {
  let selectionVC = storyboard?.instantiateViewController(withIdentifier: 
"ViewController") as! ViewController
  selectionVC.selectionDelegate = self
  present(selectionVC, animated: true, completion: nil)
}

要在其中导入游戏模式的类的扩展名：

extension ThisViewController: SpielmodusDelegate {
  func didChooseGamemode(gm: String) {
label.text = gm
  }
}

我看过一些教程并阅读了一些有关委托的内容，但我仍然不知道问题出在哪里。

Answer 1

修改

在OP中发表评论和其他信息后...

您正试图以完全错误的方式使用委托/协议。

您要做的是在“下一个”视图控制器中设置变量。

看看这个：

将第一个ViewController嵌入UINavigationController中。

第一个ViewController管理滑块。

点击“开始”按钮时，它将实例化SecondViewController并设置其 currentMode变量，然后将其推送到导航堆栈。

当您点击“真”或“敢”按钮时，它将实例化ThirdViewController并设置其 currentMode和{{ 1}}变量，然后将其压入导航堆栈。

这是示例代码：

buttonSelected

这是情节提要的源代码，因此您可以直接进入并查看其运行情况：

import UIKit

enum GameModeValues: Int {
    case Easy
    case Normal
    case Difficult
    case Extrem
}

class ViewController: UIViewController {

    @IBOutlet var theSlider: UISlider!
    @IBOutlet var gamemodeLabel: UILabel!

    var currentMode: GameModeValues = .Easy

    override func viewDidLoad() {
        super.viewDidLoad()

        theSlider.minimumValue = 0
        theSlider.maximumValue = 3.99

        theSlider.value = Float(currentMode.rawValue)

        gamemodeLabel.text = "\(currentMode)"

    }

    @IBAction func sliderChanged(_ sender: UISlider) {
        let intValue = Int(sender.value)
        if currentMode.rawValue != intValue {
            currentMode = GameModeValues(rawValue: intValue) ?? GameModeValues.Easy
            gamemodeLabel.text = "\(currentMode)"
        }
    }

    @IBAction func startButtonTapped(_ sender: Any) {
        if let vc = storyboard?.instantiateViewController(withIdentifier: "SecondViewController") as? SecondViewController {
            vc.currentMode = currentMode
            self.navigationController?.pushViewController(vc, animated: true)
        }
    }
}

class SecondViewController: UIViewController {

    var currentMode: GameModeValues = .Easy

    @IBOutlet var gamemodeLabel: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()
        gamemodeLabel.text = "\(currentMode)"
    }

    @IBAction func truthButtonTapped(_ sender: Any) {
        gotoThirdViewController("Truth")
    }

    @IBAction func dareButtonTapped(_ sender: Any) {
        gotoThirdViewController("Dare")
    }

    func gotoThirdViewController(_ truthOrDare: String) -> Void {
        if let vc = storyboard?.instantiateViewController(withIdentifier: "ThirdViewController") as? ThirdViewController {
            vc.currentMode = currentMode
            vc.buttonSelected = truthOrDare
            self.navigationController?.pushViewController(vc, animated: true)
        }
    }
}

class ThirdViewController: UIViewController {

    var currentMode: GameModeValues = .Easy
    var buttonSelected: String = "Truth"

    @IBOutlet var gamemodeLabel: UILabel!
    @IBOutlet var buttonSelectedLabel: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()
        gamemodeLabel.text = "\(currentMode)"
        buttonSelectedLabel.text = buttonSelected
    }

}

（这是最初的答案，先于评论和其他信息）

听起来/看来您有其他问题，我们在您的帖子中未看到。所以...从基础开始，以确保正确设置了协议/委托。

初始视图控制器属于<?xml version="1.0" encoding="UTF-8"?> <document type="com.apple.InterfaceBuilder3.CocoaTouch.Storyboard.XIB" version="3.0" toolsVersion="14460.31" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" useSafeAreas="YES" colorMatched="YES" initialViewController="EzF-nU-R7k"> <device id="retina4_7" orientation="portrait"> <adaptation id="fullscreen"/> </device> <dependencies> <deployment identifier="iOS"/> <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="14460.20"/> <capability name="Safe area layout guides" minToolsVersion="9.0"/> <capability name="documents saved in the Xcode 8 format" minToolsVersion="8.0"/> </dependencies> <scenes>  <scene sceneID="wYk-Om-cIK"> <objects> <viewController id="kaD-ge-RGe" customClass="ViewController" customModule="LaunchTest2" customModuleProvider="target" sceneMemberID="viewController"> <view key="view" contentMode="scaleToFill" id="EDR-jw-bbQ"> <rect key="frame" x="0.0" y="0.0" width="375" height="667"/> <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/> <subviews> <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="roundedRect" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="cEy-pg-8yn"> <rect key="frame" x="170.5" y="205" width="34" height="30"/> <state key="normal" title="Start"/> <connections> <action selector="startButtonTapped:" destination="kaD-ge-RGe" eventType="touchUpInside" id="9pa-6m-mdo"/> </connections> </button> <slider opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" value="0.5" minValue="0.0" maxValue="1" translatesAutoresizingMaskIntoConstraints="NO" id="0UU-3B-stg"> <rect key="frame" x="18" y="295" width="339" height="31"/> <connections> <action selector="sliderChanged:" destination="kaD-ge-RGe" eventType="valueChanged" id="rCT-Cq-cKf"/> </connections> </slider> <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" text="Label" textAlignment="natural" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="RIp-YU-EZ0"> <rect key="frame" x="166.5" y="385" width="42" height="21"/> <fontDescription key="fontDescription" type="system" pointSize="17"/> <nil key="textColor"/> <nil key="highlightedColor"/> </label> <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" text="View Controller" textAlignment="natural" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="kNM-Z6-BFV"> <rect key="frame" x="129" y="124" width="117" height="21"/> <fontDescription key="fontDescription" type="system" pointSize="17"/> <nil key="textColor"/> <nil key="highlightedColor"/> </label> </subviews> <color key="backgroundColor" white="1" alpha="1" colorSpace="custom" customColorSpace="genericGamma22GrayColorSpace"/> <constraints> <constraint firstItem="0UU-3B-stg" firstAttribute="leading" secondItem="V6S-9h-7yR" secondAttribute="leading" constant="20" id="1Bg-Og-bpG"/> <constraint firstItem="RIp-YU-EZ0" firstAttribute="centerX" secondItem="EDR-jw-bbQ" secondAttribute="centerX" id="GgG-qI-Zhp"/> <constraint firstItem="0UU-3B-stg" firstAttribute="top" secondItem="cEy-pg-8yn" secondAttribute="bottom" constant="60" id="MMd-ja-8TW"/> <constraint firstItem="cEy-pg-8yn" firstAttribute="top" secondItem="kNM-Z6-BFV" secondAttribute="bottom" constant="60" id="Rbo-U2-VHe"/> <constraint firstItem="kNM-Z6-BFV" firstAttribute="top" secondItem="V6S-9h-7yR" secondAttribute="top" constant="60" id="ZDi-Ou-t1c"/> <constraint firstItem="V6S-9h-7yR" firstAttribute="trailing" secondItem="0UU-3B-stg" secondAttribute="trailing" constant="20" id="n7E-Ik-Znh"/> <constraint firstItem="RIp-YU-EZ0" firstAttribute="top" secondItem="0UU-3B-stg" secondAttribute="bottom" constant="60" id="pcX-zl-Mf3"/> <constraint firstItem="cEy-pg-8yn" firstAttribute="centerX" secondItem="EDR-jw-bbQ" secondAttribute="centerX" id="sXu-6I-GZf"/> <constraint firstItem="kNM-Z6-BFV" firstAttribute="centerX" secondItem="EDR-jw-bbQ" secondAttribute="centerX" id="zKl-Us-iJy"/> </constraints> <viewLayoutGuide key="safeArea" id="V6S-9h-7yR"/> </view> <navigationItem key="navigationItem" id="qyP-ln-h7M"/> <connections> <outlet property="gamemodeLabel" destination="RIp-YU-EZ0" id="zf6-DU-NeT"/> <outlet property="theSlider" destination="0UU-3B-stg" id="7Ie-7w-jFw"/> </connections> </viewController> <placeholder placeholderIdentifier="IBFirstResponder" id="geN-ym-2yS" userLabel="First Responder" sceneMemberID="firstResponder"/> </objects> <point key="canvasLocation" x="1068" y="215.44227886056973"/> </scene>  <scene sceneID="sf5-TB-sau"> <objects> <viewController storyboardIdentifier="SecondViewController" id="h9x-Im-nTy" customClass="SecondViewController" customModule="LaunchTest2" customModuleProvider="target" sceneMemberID="viewController"> <view key="view" contentMode="scaleToFill" id="RXf-JA-XkI"> <rect key="frame" x="0.0" y="0.0" width="375" height="667"/> <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/> <subviews> <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="roundedRect" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="yLo-sI-rY9"> <rect key="frame" x="169" y="242" width="37" height="30"/> <state key="normal" title="Truth"/> <connections> <action selector="truthButtonTapped:" destination="h9x-Im-nTy" eventType="touchUpInside" id="5xP-1e-c08"/> </connections> </button> <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="roundedRect" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="8BM-bn-86x"> <rect key="frame" x="171" y="332" width="33" height="30"/> <state key="normal" title="Dare"/> <connections> <action selector="dareButtonTapped:" destination="h9x-Im-nTy" eventType="touchUpInside" id="njl-le-CMY"/> </connections> </button> <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" text="Second View Controller" textAlignment="natural" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="3Od-JO-yEA"> <rect key="frame" x="97.5" y="80" width="180" height="21"/> <fontDescription key="fontDescription" type="system" pointSize="17"/> <nil key="textColor"/> <nil key="highlightedColor"/> </label> <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" text="Game Mode Label" textAlignment="natural" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="Uct-vv-SSq"> <rect key="frame" x="118" y="161" width="139" height="21"/> <fontDescription key="fontDescription" type="system" pointSize="17"/> <nil key="textColor"/> <nil key="highlightedColor"/> </label> </subviews> <color key="backgroundColor" white="1" alpha="1" colorSpace="custom" customColorSpace="genericGamma22GrayColorSpace"/> <constraints> <constraint firstItem="8BM-bn-86x" firstAttribute="centerX" secondItem="RXf-JA-XkI" secondAttribute="centerX" id="Hrm-TE-ocS"/> <constraint firstItem="Uct-vv-SSq" firstAttribute="top" secondItem="3Od-JO-yEA" secondAttribute="bottom" constant="60" id="cky-Ow-tOC"/> <constraint firstItem="8BM-bn-86x" firstAttribute="top" secondItem="yLo-sI-rY9" secondAttribute="bottom" constant="60" id="d8A-4y-Tt7"/> <constraint firstItem="yLo-sI-rY9" firstAttribute="top" secondItem="Uct-vv-SSq" secondAttribute="bottom" constant="60" id="f3t-gw-hg7"/> <constraint firstItem="3Od-JO-yEA" firstAttribute="top" secondItem="LzW-mg-KAw" secondAttribute="top" constant="60" id="iKq-Nc-Wpn"/> <constraint firstItem="Uct-vv-SSq" firstAttribute="centerX" secondItem="RXf-JA-XkI" secondAttribute="centerX" id="oAh-7Z-5Uc"/> <constraint firstItem="3Od-JO-yEA" firstAttribute="centerX" secondItem="RXf-JA-XkI" secondAttribute="centerX" id="rcc-r2-6jz"/> <constraint firstItem="yLo-sI-rY9" firstAttribute="centerX" secondItem="RXf-JA-XkI" secondAttribute="centerX" id="ubo-Xt-2bT"/> </constraints> <viewLayoutGuide key="safeArea" id="LzW-mg-KAw"/> </view> <connections> <outlet property="gamemodeLabel" destination="Uct-vv-SSq" id="gez-Ie-G4n"/> </connections> </viewController> <placeholder placeholderIdentifier="IBFirstResponder" id="IIe-79-ZbY" userLabel="First Responder" sceneMemberID="firstResponder"/> </objects> <point key="canvasLocation" x="1746" y="215"/> </scene>  <scene sceneID="Gj0-Xb-uvT"> <objects> <navigationController automaticallyAdjustsScrollViewInsets="NO" id="EzF-nU-R7k" sceneMemberID="viewController"> <toolbarItems/> <navigationBar key="navigationBar" contentMode="scaleToFill" insetsLayoutMarginsFromSafeArea="NO" id="c80-8v-3ra"> <rect key="frame" x="0.0" y="20" width="375" height="44"/> <autoresizingMask key="autoresizingMask"/> </navigationBar> <nil name="viewControllers"/> <connections> <segue destination="kaD-ge-RGe" kind="relationship" relationship="rootViewController" id="LEe-hD-Fyl"/> </connections> </navigationController> <placeholder placeholderIdentifier="IBFirstResponder" id="5UX-yJ-buo" userLabel="First Responder" sceneMemberID="firstResponder"/> </objects> <point key="canvasLocation" x="370" y="215"/> </scene>  <scene sceneID="XIm-bw-14T"> <objects> <viewController storyboardIdentifier="ThirdViewController" id="Sg0-vM-Ir7" customClass="ThirdViewController" customModule="LaunchTest2" customModuleProvider="target" sceneMemberID="viewController"> <view key="view" contentMode="scaleToFill" id="eVd-jb-0fY"> <rect key="frame" x="0.0" y="0.0" width="375" height="667"/> <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/> <subviews> <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" text="Third View Controller" textAlignment="natural" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="txR-9a-ybO"> <rect key="frame" x="107" y="80" width="161" height="21"/> <fontDescription key="fontDescription" type="system" pointSize="17"/> <nil key="textColor"/> <nil key="highlightedColor"/> </label> <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" text="Game Mode Label" textAlignment="natural" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="2M0-8h-jtQ"> <rect key="frame" x="118" y="161" width="139" height="21"/> <fontDescription key="fontDescription" type="system" pointSize="17"/> <nil key="textColor"/> <nil key="highlightedColor"/> </label> <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" text="Button Selected Label" textAlignment="natural" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="Zug-Dn-13z"> <rect key="frame" x="103" y="242" width="169" height="21"/> <fontDescription key="fontDescription" type="system" pointSize="17"/> <nil key="textColor"/> <nil key="highlightedColor"/> </label> </subviews> <color key="backgroundColor" white="1" alpha="1" colorSpace="custom" customColorSpace="genericGamma22GrayColorSpace"/> <constraints> <constraint firstItem="2M0-8h-jtQ" firstAttribute="centerX" secondItem="eVd-jb-0fY" secondAttribute="centerX" id="Eoi-YU-vc6"/> <constraint firstItem="Zug-Dn-13z" firstAttribute="top" secondItem="2M0-8h-jtQ" secondAttribute="bottom" constant="60" id="EtH-T4-MD5"/> <constraint firstItem="txR-9a-ybO" firstAttribute="top" secondItem="BOa-UN-1aS" secondAttribute="top" constant="60" id="nyi-KX-pGE"/> <constraint firstItem="txR-9a-ybO" firstAttribute="centerX" secondItem="eVd-jb-0fY" secondAttribute="centerX" id="qOD-65-vLb"/> <constraint firstItem="Zug-Dn-13z" firstAttribute="centerX" secondItem="eVd-jb-0fY" secondAttribute="centerX" id="rZa-Xu-pzH"/> <constraint firstItem="2M0-8h-jtQ" firstAttribute="top" secondItem="txR-9a-ybO" secondAttribute="bottom" constant="60" id="wrI-a0-ak4"/> </constraints> <viewLayoutGuide key="safeArea" id="BOa-UN-1aS"/> </view> <connections> <outlet property="buttonSelectedLabel" destination="Zug-Dn-13z" id="GLO-r2-gY6"/> <outlet property="gamemodeLabel" destination="2M0-8h-jtQ" id="Ay0-dI-rmU"/> </connections> </viewController> <placeholder placeholderIdentifier="IBFirstResponder" id="TPA-ns-oaF" userLabel="First Responder" sceneMemberID="firstResponder"/> </objects> <point key="canvasLocation" x="2447" y="215"/> </scene> </scenes> </document>类。它有一个连接到ThisViewController的按钮。

另一个视图控制器属于@IBAction func chooseButtonTapped(_ sender: UIButton)类。它具有连接到ViewController的{{1}}（确保其Storyboard ID为 ViewController ）。

使用此代码：

UISlider

并运行该应用。

点击按钮应显示@IBAction func gamemodeSliderChanges(_ sender: UISlider)和滑块。拖动滑块时，您应该在调试控制台中看到重复的打印内容：

import UIKit

protocol SpielmodusDelegate: class {
    func didChooseGamemode(gm: String)
}

class ViewController: UIViewController {

    // use weak var for the delegate
    weak var selectionDelegate: SpielmodusDelegate?

    @IBAction func gamemodeSliderChanges(_ sender: UISlider) {
        if sender.value > 0.8 {
            selectionDelegate?.didChooseGamemode(gm: "Extrem")
        } else {
            selectionDelegate?.didChooseGamemode(gm: "Normal")
        }
    }

}

class ThisViewController: UIViewController {

    @IBAction func chooseButtonTapped(_ sender: UIButton) {
        if let vc = storyboard?.instantiateViewController(withIdentifier: "ViewController") as? ViewController {
            vc.selectionDelegate = self
            present(vc, animated: true, completion: nil)
        }
    }

}

extension ThisViewController: SpielmodusDelegate {
    func didChooseGamemode(gm: String) {
        print("Received: " + gm)
    }
}

应该可以。如果可以，请将其与您当前项目的设置方式进行比较。

为什么此委托代码出错？

1 个答案: