ios - 委托(delegate)创建 ViewController 的新实例

Question

我通过委托(delegate)方法将数据发送到 View Controller 。在接收数据的 View Controller 中，如果我在 viewDidLoad 中 print(self) 我得到这个值:

<PageViewControllerImage: 0x7fba16d0dc40>

如果我在委托(delegate)函数中print(self)，我会得到这个值:

<PageViewControllerImage: 0x7fba16e0eab0>

我相信这就是我定义委托(delegate)的方式，它正在创建 PageViewControllerImage 的新实例，但我不知道如何获取对它的现有引用？

这就是我用来在发送数据的类中设置委托(delegate)的方法:

self.indexDelegate = PageViewControllerImage()

------编辑--------

我正在尝试从我的 PageViewController 类发送数据:

var indexDelegate: GetMyIndexDelegate?



func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
    if (completed && finished) {
        if let currentVC = pageViewController.viewControllers?.last {
            let index = vcArr.index(of: currentVC)

            if index == 3 {

                // call the delegate function in delegate class
                indexDelegate?.getIndex(index: index!)

            }
        }
    }
}

override func viewDidLoad() {
    super.viewDidLoad()

    // just been trying to define instance first
    let storyboard: UIStoryboard = UIStoryboard (name: "Main", bundle: nil)
    let PageViewControllerImageInstance: PageViewControllerImage = storyboard.instantiateViewController(withIdentifier: "vc4") as! PageViewControllerImage
    print("Defined Instance \(PageViewControllerImageInstance)")
    self.indexDelegate = PageViewControllerImageInstance

然后在类PageViewControllerImage中接收数据:

protocol GetMyIndexDelegate {
    func getIndex(index: Int)
}

import UIKit

class PageViewControllerImage: UIViewController, GetMyIndexDelegate {

//delegate functionto get index
func getIndex(index: Int) {
    if index == 3 {
        print("Inside delegate: \(self)")

    }
}

@IBOutlet var signupImage: UIImageView!

override func viewDidLoad() {
    super.viewDidLoad()

    print("viewDidLoad: \(self)")

    // Do any additional setup after loading the view.
}

即使在设置委托(delegate)之前定义了 viewController 的实例，它仍然返回不同的实例号:

Defined Instance <ParseStarterProject_Swift.PageViewControllerImage: 0x7fb365f06260>

viewDidLoad: <ParseStarterProject_Swift.PageViewControllerImage: 0x7fb365d0c940>

Inside delegate: <ParseStarterProject_Swift.PageViewControllerImage: 0x7fb365f06260>

Answer 1

委托(delegate)通常是在外部设置的，并且应该是可选的。

我假设indexDelegate是ViewController上的一个属性。您应该在转换到 PageViewControllerImage 实例时设置委托(delegate)。

根据您转换到 PageViewControllerImage Controller 的方式，可以通过多种方式实现这一点。

如果您设置了 Storyboard Segue，则可以在 prepareForSegue 中设置委托(delegate)。例如:

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "showPageViewControllerImage" {
        guard let pageViewControllerImage = segue.destination as? PageViewControllerImage
        else {
            return
        }
        self.delegate = pageViewControllerImage
    }
}

或者，如果您手动转换到新 Controller ，则可以将委托(delegate)设置为该实例。