如何从两个中清除一个pickerView？

Question

我有两个pickerView，当用户在第二个pickerView 加载后选择第一个时。但是，如果用户再次执行此操作，则所有数据都将附加到第二个 pickerView。当用户选择第一个时，我必须清除第二个 pickerView 内容。我正在使用 reloadAllComponents() 方法，但它不起作用。

我的代码；

    var country_array = [String]()
    var countryIds_array = [String]()
    var city_array = [String]()
    var cityIds_array = [String]()

    override func viewDidLoad() {
        super.viewDidLoad()
        getCountry()
    }

func getCountry(){
        //var hata = false
        print("Getting Country List")
        let query = PFQuery(className: "cls_ulke")
        query.limit = 300
        query.order(byDescending: "oncelik")
        query.findObjectsInBackground { (objects: [PFObject]?, error) -> Void in
            if error == nil {
                print("Getted!")
                print("Looping------------------>")
                if let objects = objects {
                    for object in objects{
                        print(object.objectId ?? "BOŞ")
                        print(object["ulke_adi"])
                        self.country_array.append(object["ulke_adi"] as! String)
                        self.countryIds_array.append(object.objectId!)
                    }
                    self.pckerview.delegate = self
                    self.pckerview.dataSource = self
                }
                print("<-------------------Looped")
            }else{
                print("HATA")
            }
        }
    }

    func getCities(objectID:String){
        print("Getting City List")
        let query = PFQuery(className: "cls_il")
        query.limit = 1000
        query.order(byDescending: "oncelik")
        query.whereKey("ulke_ID", equalTo: PFObject(withoutDataWithClassName: "cls_ulke", objectId: objectID))
        query.findObjectsInBackground { (objects:[PFObject]?, error) in
            if error == nil {
                print("Getted!")
                print("Looping------------------>")
                if let objects = objects {
                    for object in objects {
                        print(object["il_adi"])
                        self.city_array.append(object["il_adi"] as! String)
                        self.cityIds_array.append(object.objectId!)
                    }
                    self.pckerview2.reloadAllComponents()
                    self.pckerview2.delegate = self
                    self.pckerview2.dataSource = self
                }
                print("<-------------------Looped")
            }else{
                print("HATA")
            }
        }
    }

    func numberOfComponents(in pickerView: UIPickerView) -> Int {
        return 1
    }

    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        var donecek = 0
        if pickerView == pckerview {
            donecek = country_array.count
        }else if pickerView == pckerview2{
            donecek = city_array.count
        }
        return donecek
    }

    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        var donecek = ""
        if pickerView == pckerview {
            donecek = country_array[row]
        }else if pickerView == pckerview2{
            donecek = city_array[row]
        }
        return donecek
    }

    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
        if pickerView == pckerview {
            tfield.text = countryIds_array[row]
            getCities(objectID:countryIds_array[row])

        }
    } 

Answer 1

reloadAllComponents() 正在调用您的代理进行重新加载。来自documentation：

调用此方法会导致选取器视图向委托查询所有组件的新数据。

但是，您的代码显示您只在其后设置了pckerview2.delegate。

self.pckerview2.reloadAllComponents()
self.pckerview2.delegate = self
self.pckerview2.dataSource = self

所以我的猜测是reloadAllCompontents() 没有设法查询代理，因为它是nil。（除非您已将其设置在其他位置）尝试将其移至下方：

self.pckerview2.delegate = self
self.pckerview2.dataSource = self 
self.pckerview2.reloadAllComponents()

第二种可能性是您没有清除city_array，因此您总是将城市附加到它。如果是这种情况，在for 循环之前添加一个removeAll()。像这样的：

print("Looping------------------>")
    if let objects = objects {
        self.city_array.removeAll()
        self.cityIds_array.removeAll()

        for object in objects {
        // rest of the codes