ios - 从另一个类加载函数在 Swift IOS 中崩溃

Question

我想在导航 Controller 弹回 ViewController1 之前从我的 ViewController 2 加载函数 checkStatus()(它是我的 ViewController1 的一部分)。
不幸的是，在调用该函数时，应用程序一加载就崩溃了，我真的很沮丧，因为我不知道自己做错了什么。
ViewController 嵌入在导航 Controller 中。
ViewController1 中的代码:

func checkStatus(){
/* setting Label texts (Outlets) to a specific value but it is 
irrelevant as the compiler does not even get to 
    this point. The program crashes as soon as the function is called (tried it with prints).*/

ViewController2 中的代码:

@IBAction func didTapBack(_ sender: UIButton){
// first the function is animating something inside the VC2
ViewController1().checkStatus() // function gets called here
self.navigationController?.popToRootViewController(animated: false)
}

我很感激任何帮助。

Answer 1

您可以使用委托(delegate)模式在您的情况下调用函数。
View Controller 代码:

import UIKit

class ViewController: UIViewController, SecondViewControllerDelegate {

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view.
    
}

@IBAction func gotoSecondVC(_ sender: UIButton) {
    
    let secondVC = self.storyboard?.instantiateViewController(identifier: "SecondViewController") as! SecondViewController
    secondVC.delegate = self
    self.navigationController?.pushViewController(secondVC, animated: true)
    
}

func checkStatus() {
    print("\(#function) called...")
}

}

SecondViewController 代码:

import UIKit

protocol SecondViewControllerDelegate: class {
    func checkStatus()
}

class SecondViewController: UIViewController {

    weak var delegate: SecondViewControllerDelegate?

    override func viewDidLoad() {
        super.viewDidLoad()

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

    @IBAction func backButtonTapped(_ sender: UIButton) {
        delegate?.checkStatus()
        self.navigationController?.popViewController(animated: true)
    }

}