swift - Xcode Swift 3 选择器 : Putting the DataSource in ViewDidLoad

Question

我正在尝试设置一个选择器，它会根据某些条件显示不同的结果。唯一的问题是我需要将 dataSource (将显示的选择器数据)放在 viewDidLoad 之外。如果满足条件，我需要 viewDidLoad 来加载适当的数据。但是，对于我见过的处理选择器的代码，似乎 dataSource 数组放置在 viewDidLoad 之外(我认为委托(delegate)方法可以使用该值)。我只是想知道是否可以将此 dataSource 放入 viewDidLoad 中，以便它能够识别它，或者是否有办法在 之外运行 Switch 或 If 语句>viewDidLoad 并在类中。

import UIKit
import Parse

class VC: UIViewController, UIPickerViewDataSource, UIPickerViewDelegate {

    var pickerData = [String]()

    @IBOutlet weak var namePicker: UIPickerView!

    override func viewDidLoad() {
        super.viewDidLoad()

        namePicker.dataSource = self
        namePicker.delegate = self


        //here I want the picker to show something different depending on the value of nameOfPerson. I changed the order of the array because the picker selects the first name of the array as the default. 
        switch nameOfPerson
        {
        case "Carly": 
            let pickerData = ["Carly","Jeff","Bob","Anita"]
        case "Jeff": 
            let pickerData = ["Jeff","Carly","Bob","Anita"]
        case "Bob": 
            let pickerData = ["Bob","Carly","Jeff","Anita"]
        case "Anita": 
            let pickerData = ["Anita","Carly","Jeff","Bob"]
        }
    }
   func numberOfComponents(in pickerView: UIPickerView) -> Int {
    return 1
    }
    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
    return pickerData.count
    }
    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
    return pickerData[row]
    }
    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int)
    {

    }
}

Answer 1

I am just wondering if I can place this dataSource into viewDidLoad so that it would recognize it, or if there was a way to run a Switch or If statement outside the viewDidLoad and in the class

没有。数据源方法必须是方法，即位于类顶层的函数，以便 Objective-C 能够看到它们。因此，数据本身必须对数据源方法可见，并且在 viewDidLoad 和数据源方法之间共享数据的唯一连贯方式是作为属性，例如 var pickerData >.

你的代码有什么问题是let:

    case "Carly": 
        let pickerData = ["Carly","Jeff","Bob","Anita"]
    case "Jeff": 
        let pickerData = ["Jeff","Carly","Bob","Anita"]
    case "Bob": 
        let pickerData = ["Bob","Carly","Jeff","Anita"]
    case "Anita": 
        let pickerData = ["Anita","Carly","Jeff","Bob"]
    }

从每个案例中删除术语let!否则，您只是设置一个临时局部变量 pickerData，这不是您想要做的。您想要设置您声明的属性，如下所示:

var pickerData = [String]()

...而你的代码没有这样做!你想要的是这样的:

case "Carly": 
    self.pickerData = ["Carly","Jeff","Bob","Anita"]
case "Jeff": 
    self.pickerData = ["Jeff","Carly","Bob","Anita"]
case "Bob": 
    self.pickerData = ["Bob","Carly","Jeff","Anita"]
case "Anita": 
    self.pickerData = ["Anita","Carly","Jeff","Bob"]
}

(当然，您还需要一个 default 案例。)

最后，为了安全起见，重新加载数据:

self.namePicker.reloadAllComponents()