PresentViewController在instantiateViewController上找到nil值

Question

 func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        if collectionView.tag == 2{

            switch indexPath.item {
            case 0:
               if let vc = storyboard?.instantiateViewController(withIdentifier: "offersScreen") as? OffersVC {
                vc.cityID = self.cityID!
                vc.categoryID = indexPath.item + 1
                vc.headingLBL.text =  self.names[indexPath.item]
                vc.cityLBL.text = self.selectCity.text!
                    present(vc, animated: true, completion: nil)
                }   
            case 1:
                print("You're heading VC 1!")
            case 2:
                print("You're heading VC 2!")
            case 3:
                print("You're heading VC 3!")
            default:
                print("Something went wrong")
            }
        }
    }

enter image description here

我把一切都写了完美的idk我弄错了。目前发现零值。我从标签栏viewController呈现viewcontroller具有4个值请帮助或指导。预先感谢。

Answer 1

原因是所有出口都为零，直到vc加载为止

选项＃1

 vc.loadViewIfNeeded()
 vc.headingLBL.text =  self.names[indexPath.item]

选项＃2

制作需要发送的内容

class OffersVC:UIViewController {
   var sendedStr = ""

然后在viewDidLoad内

self.headingLBL = sendedStr

Answer 2

[查看您的图像描述，我认为问题是您试图在不首先对其进行初始化的情况下展开'headingLBL'。

请参见Swift Xcode "EXC_BAD_INSTRUCTION"