Question

我有2个类，我尝试使用NotificationsCenter和Observers发送布尔值。如果布尔值发送正确，那么我想在ViewController上导航。但是很不幸，由于某些原因，我从Observer（checkIsUserFromChecklist）开始的功能未触发。这是我的代码：

extension Notification.Name {
    static let isAccessedFromChecklistVC = Notification.Name(rawValue: "isAccessedFromChecklistVC")
}

// Class where I want to check if the boolean is changed
class ChecklistVC: UIViewController {

    var isAccessedFromChecklist = true

    override func viewDidLoad() {
        super.viewDidLoad()
        NotificationCenter.default.post(name: .isAccessedFromChecklistVC, object: isAccessedFromChecklist)
    }
    //…
    //…
    //…
}

// Class where I want to get the value of the boolean

class FullscreenImageVC: UIViewController {

    var isAccessedFromChecklistVC = false

    // Remove observer from memory after we use it
    deinit {
        NotificationCenter.default.removeObserver(self)
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        createObservers()
    }

    func createObservers(){

        NotificationCenter.default.addObserver(self,
                                               selector: #selector(checkIfIsAccessedFromChecklist),
                                               name: .isAccessedFromChecklistVC,
                                               object: nil)
    }

    @objc func checkIfIsAccessedFromChecklist(_ notification: Notification){

        if let object = notification.object as? Bool{
            print("Object status: \(object)") // Is never entering here.

            isAccessedFromChecklistVC = object
        }
    }

    func navigateToChecklist(){

        if isAccessedFromChecklistVC == true {
            let checklistVC = self.storyboard?.instantiateViewController(withIdentifier: "ChecklistVC") as! ChecklistVC
            self.navigationController?.setViewControllers([self.navigationController!.viewControllers.first!, checklistVC], animated: true)
        }
    }
}

感谢您阅读。

Answer 1

该帖子似乎是

NotificationCenter.default.post(name: .isAccessedFromChecklistVC, object: isAccessedFromChecklist)

在FullscreenImageVC vc注册为观察者之前

NotificationCenter.default.addObserver(self,
                 selector: #selector(checkIfIsAccessedFromChecklist),
                 name: .isAccessedFromChecklistVC
                 object: nil)

因此，请确保在第二个vc处于活动状态时进行发布

使用NotificationCenter和Observer在UIViewController之间发送布尔值

1 个答案: