视图控制器按钮，用于重新加载另一个表视图控制器的数据

Question

请原谅我提出了一个简单的问题，因为我已经阅读了很多解决方案，但仍然不知道如何解决。

如果按钮在同一类中，则可以成功运行TutorListViewController上的以下代码，并调用函数observeEnglishCases（）。但是，当我尝试在不同的类和视图控制器中执行此操作时，当我在刺激器中轻按按钮时，应用程序崩溃并显示以下代码：线程1：致命错误：在展开一个可选值（并且它不是重复的问题）

有人会在几天后未能做到这一点让我难过吗。

这是ViewController1上的代码：

@IBAction func englishGO(_ sender: Any) {
    self.tabBarController?.selectedIndex = 1
    let tutorVC = storyboard?.instantiateViewController(withIdentifier: "TutorListViewController") as? TutorListViewController
    tutorVC!.observeEnglishCases()
    }

以下是TutorListViewController上的代码：

  override func viewDidLoad() {
    super.viewDidLoad()

    observeEnglishCases()

   }

func observeEnglishCases(){
    let casesRef = Database.database().reference().child("cases")
    let queryRef = casesRef.child("school").queryEqual(toValue: "ling")
    queryRef.observe(.value, with: { snapshot in

        var tempPosts = [Case]()


        for child in snapshot.children {
            if let childSnapshot = child as? DataSnapshot,
                let dict = childSnapshot.value as? [String:Any],
                let name = dict["name"] as? String,
                let gender = dict["gender"] as? String,
                let school = dict["school"] as? String,
                let year = dict["year"] as? String,
                let major = dict["major"] as? String,
                let tutorsubject = dict["tutorsubject"] as? String,
                let tutoryear = dict["tutoryear"] as? String,
                let tutorperformance = dict["tutorperformance"] as? String,
                let region = dict["region"] as? String,
                let minimumprice = dict["minimumprice"] as? String,
                let thingtospeak = dict["thingtospeak"] as? String,
                let photoURL = dict["photoURL"] as? String,
                let url = URL(string:photoURL){
                let caser = Case(name: name, gender: gender, school: school, year: year, major: major, tutorsubject: tutorsubject, tutoryear: tutoryear, tutorperformance: tutorperformance, region: region, minimumprice: minimumprice, thingtospeak: thingtospeak, photoURL: url)
                tempPosts.insert(caser, at:0)
            }
        }
        self.cases = tempPosts
       self.tutorCasesCollectionView.reloadData() //App Crashed Here
    })




}