Question

我有两个不同的ViewControllers，细节＆amp;搜索。转到详细信息的segues工作正常，但进入搜索的人不断崩溃应用程序。我花了两个小时阅读类似的问题，但似乎没有一个问题有同样的问题：

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

    let detailVC = segue.destination as! DetailViewController

    if segue.identifier == "newDocSegue"   {
        // Create a new document and pass it to the detail view.
        detailVC.doc = Document()
        detailVC.isAddAction = true
    }

    if segue.identifier == "editDocSegue"    {
        // Load the existing document into the detail view, for editing.
        let indexPath = tableView.indexPath(for: sender as! UITableViewCell)!
        detailVC.doc = Document[indexPath.row]
        detailVC.isAddAction = false
    }
     else if segue.identifier == "searchSegue" {
        shouldPerformSegue(withIdentifier: "searchSegue", sender: Any?.self)
    }

}

Answer 1

你的问题是

让detailVC = segue.destination为！ DetailViewController

线。这将尝试将任何VC（包括您的搜索VC）转换为DetailViewController。试试这个：

let detailVC : UIViewController

if segue.identifier == "newDocSegue"   {
    // Create a new document and pass it to the detail view.
    detailVC = segue.destination as! DetailViewController
    detailVC.doc = Document()
    detailVC.isAddAction = true
}

if segue.identifier == "editDocSegue"    {
    // Load the existing document into the detail view, for editing.
    detailVC = segue.destination as! ???  // not sure what type you want here
    let indexPath = tableView.indexPath(for: sender as! UITableViewCell)!
    detailVC.doc = Document[indexPath.row]
    detailVC.isAddAction = false
}
 else if segue.identifier == "searchSegue" {
    detailVC = segue.destination as! SearchViewController
    shouldPerformSegue(withIdentifier: "searchSegue", sender: Any?.self)
}

Answer 2

您的问题出在：

let detailVC = segue.destination as! DetailViewController

如果目的地的类型为SearchViewController，则会导致错误

试试这个：

if let detailVC = segue.destination as? DetailViewController

您应该了解as?和as!

Xcode Segue＆＃34;无法转换类型＆＃34;

2 个答案: