ios - 从另一个类(class) swift 获得 IBOutlet

Question

我在 Main_Screen 类中有一个 IBOutlet，它在连接到具有 ScrollView 的主 ViewController 的类中可用，但如果我尝试获取它，则返回 nil

View Controller 中的代码

import UIKit

class ViewController: UIViewController , UIScrollViewDelegate {

    @IBOutlet weak var scrollVieww: UIScrollView!

    override func viewDidLoad() {
         super.viewDidLoad()

      self.scrollVieww.pagingEnabled = true
      self.scrollVieww.delegate = self

        let storyboard = UIStoryboard(name: "Main", bundle: nil)
        if let vc = storyboard.instantiateViewControllerWithIdentifier("MainScreen") as? Main_Screen {
            // imageview returns nil :(
            let imageView = vc.avatarImageView
        }

      // Do any additional setup after loading the view, typically from a nib.
        let V1 = self.storyboard?.instantiateViewControllerWithIdentifier("HomeScreen") as UIViewController!
        //Add initialized view to main view and its scroll view and also set bounds
        self.addChildViewController(V1)
        self.scrollVieww.addSubview(V1.view)
        V1.didMoveToParentViewController(self)
        V1.view.frame = scrollVieww.bounds

        //Initialize using Unique ID for the View
        let V2 = self.storyboard?.instantiateViewControllerWithIdentifier("MainScreen") as UIViewController!
        //Add initialized view to main view and its scroll view also set bounds
        self.addChildViewController(V2)
        self.scrollVieww.addSubview(V2.view)
        V2.didMoveToParentViewController(self)
        V2.view.frame = scrollVieww.bounds

        //Create frame for the view and define its urigin point with respect to View 1
        var V2Frame: CGRect = V2.view.frame
        V2Frame.origin.x = self.view.frame.width
        V2.view.frame = V2Frame

      //The width is set here as we are dealing with Horizontal Scroll
        //The Width is x3 as there are 3 sub views in all
        self.scrollVieww.contentSize = CGSizeMake((self.view.frame.width) * 2, (self.view.frame.height))

 }

Answer 1

简短回答:不要那样做。您应该将另一个 View Controller 的 View 视为私有(private) View 。

如果您需要操作另一个 View Controller 的 UI，请添加用于请求 UI 更改的公共(public)方法，然后让 VC 中的代码进行更改。

这都是更好的设计，并且它避免了其他 View Controller 的 View 尚未创建的情况，因此它们为 nil 并且它失败/崩溃并显示“在尝试展开可选时遇到 nil”消息。