關閉 Viewcontroller 時傳遞數據

Question

我想把數據傳遞給根視圖控制器，也就是前一個ViewController后的ViewController ，我選擇使用delegation的方式解決這個問題：Scheme：

視圖控制器 -> 搜索視圖控制器

SearchViewController生成數據並關閉

class ViewController: UIViewController, IsAbleToReceiveData {    
@IBAction func addButton_touchUpInside(_ sender: UIButton) {
        performSegue(withIdentifier: "gotoSearchViewController", sender: nil)
    }

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "gotoSearchViewController" {
        let vc2 = SearchViewController()
        vc2.delegate = self
    }
}


func passData(city: cityObject) {
        print(city.cityName)

    }
}

協議聲明如下：

protocol IsAbleToReceiveData: class {
   func passData(city : cityObject)
}

在SearchViewController我有：

weak var delegate: IsAbleToReceiveData?

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    let citySelected: cities?
    citySelected = self.citiesQueried[indexPath.row]
    RequestAPI.convertData(city: citySelected!) { (city) in

        self.delegate?.passData(city: city)
    }
    dismiss(animated: true, completion: nil)
}

當我嘗試在ViewController的函數中打印數據時，即使SearchViewController convertData方法返回一個 cityObject，也沒有打印任何內容。 解散后如何將數據傳遞給ViewController ？

Answer 1

代替

 let vc2 = SearchViewController()
 vc2.delegate = self

和

 if let vc2 = segue.destination as? SearchViewController {
    vc2.delegate = self
 }

Answer 2

嘗試

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
   if let searchVC = segue.destination as? SearchViewController {
      searchVC.delegate = self
}