ios - Swift 4 委托(delegate)不适用于标签栏 Controller

Question

我有一个带有 4 个 View 的标签栏 View Controller ，我在第 4 个 View 上设置了一个协议(protocol)，并使第一个 View 符合这个协议(protocol)。当我从第 4 个 View 调用委托(delegate)方法时，它不起作用，并且第 1 个和第 4 个 View Controller 之间没有 segue。

我已经定义了我的协议(protocol) 并设置 weak var delegate: delegateProtocol? 然后在第一个 View Controller 中我做了以下操作

class VC1: delegateProtocol {
    viewdidLoad(){
    var vc4 = VC4()
    VC4.delegate = self
  }

这是第四个 View Controller 的片段

protocol SettingsDelegate: class {
    func locationDidSet(location: CLLocation)
}


class VC4: UIViewController {


  weak var delegate: SettingsDelegate?
 let controller = LocationPickerViewController()
 let navigationController = UINavigationController(rootViewController: controller)
 present(navigationController, animated: true, completion: nil)
  controller.completion = { location in
                self.location = location?.title ?? "Not found"
                defaults.set(location: location!.location, forKey: "location")
                self.tableView.reloadData()
                self.delegate?.locationDidSet(location: location!.location)
            }

这是第一个 ViewController 的片段

class MainVC: UIViewController, SettingsDelegate {
    func locationDidSet(location: CLLocation) {
        print(location.coordinate.latitude)
    }

  override func viewDidLoad() {
        super.viewDidLoad()
        settingVC = SettingsVC()
        settingVC?.delegate = self
}
}

Answer 1

在 MainVC 的 viewDidLoad 中，您正在创建一个新的 SettingsVC 实例并将 self 分配给该实例的属性.不是标签栏 Controller 的实际第四 View Controller 。

从 tabBarController?.viewControllers 数组中获取第四个 View Controller 实例，并将 self 分配给它的 delegate 属性

//主VC

override func viewDidLoad() {
  super.viewDidLoad()
  if let settingVC = self.tabBarController?.viewControllers?.first(where: { $0 is SettingsVC }) as? SettingsVC {
    settingVC.delegate = self
  }
}

如果 View Controller 嵌入在导航 Controller 中。

//更新

if let settingsNavVC = self.tabBarController?.viewControllers?.first(where: { $0 is UINavigationController }) as? UINavigationController, 
    let settingsVC = settingsNavVC.rootViewController as? SettingsVC {
        settingsVC.delegate = self
}