UINavigationController return 无 Swift

Question

当我在 viewWillApear 或 viewDidLoad 中尝试 print(self.navigationController) 时，一切正常。但是当委托 return 来自 API print(self.navigationController) return nil 的响应时。可能是什么？

extension EnterpriseList: APIDataDelegate {
    func successRequest() { //print(self.navigtionController) == nil
        DispatchQueue.main.async {
            self.navigationController?.popToRootViewController(animated: true)
        }
    }

    func badRequest() {
        DispatchQueue.main.async {
            Alert.showWarningAlert(withTitle: "Внимание!", andMessage: "Ошибка получения данных, попробуйте чуть позже", whereSender: self)
        }
    }

}

Answer 1

class EnterpriseList: UIViewController {
     let dataSource = DataSource()

     override func viewDidLoad() {
        super.viewDidLoad()
        dataSource.delegate = self
        dataSource.makeAPICall()
     }
  }

   extension EnterpriseList: APIDataDelegate {
      func successRequest() {
          DispatchQueue.main.async {
            self.navigationController!.popToRootViewController(animated: true)
        }
   }

   func badRequest() {
      DispatchQueue.main.async {
      }
   }
}

protocol APIDataDelegate: class {
    func successRequest()
    func badRequest()
}

class DataSource {
    var delegate: APIDataDelegate?

    private let queue = DispatchQueue(label: "Test", qos: .background, attributes: [], autoreleaseFrequency: .inherit, target: nil)

    func makeAPICall() {
        queue.asyncAfter(deadline: .now() + 2) {[weak self] in
            self?.delegate?.successRequest()
        }
        queue.asyncAfter(deadline: .now() + 10) {[weak self] in
            self?.delegate?.successRequest()
        }
    }
}

崩溃是因为您在已释放的对象上调用方法。

解决方法如下：让你的代表很弱，你正在正确地释放对象

weak var delegate: APIDataDelegate?

Answer 2

感谢@Manoj 的回答，它对我有帮助。但我在其他地方找到了解决方案。除了 SurveyList，我还有 UserMenu，我在其中创建了 static let 视图控制器。删除 static 我解决了我的问题。

UINavigationController return 无 Swift

UINavigationController return nil Swift

api

delegates

ios

swift

swift5