Question

我有以下课程，我正在试着。

class FriendsProfileViewController: UIViewController {
    var user : User!

    override func viewDidLoad() {
        super.viewDidLoad()
        print(user.firstName)
    }
}

在segueing类中，我做了以下传递数据

var friends: [User]?

override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
    performSegueWithIdentifier("viewFriend", sender: indexPath)
}

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    let destinationVC = segue.destinationViewController
    if let friendsProfileVC = destinationVC as? FriendsProfileViewController{
        if let indexPath = sender as? NSIndexPath{
            print(indexPath.row)
            friendsProfileVC.user = friends?[indexPath.row]
        }
    }
}

为什么我收到错误

致命错误：在解包可选值时意外发现nil

即使我的friend?[indexPath.row]被证实包含了一个值，当我提出错误时。

Answer 1

在执行segue之前尝试获取用户并将其作为segue发送者传递。

var friends: [User]?

private func friend(at index: Int) -> User? {

    return friends.flatMap { $0.indicies.contains(index) ? $0[index] : nil }
}

override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {

    if let friend = friend(at: indexPath.row) {
        performSegueWithIdentifier("viewFriend", sender: friend)
    } else {
        print("Invalid index: \(indexPath.row)")
    }
}

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {

    switch (segue.destinationViewController, sender) {
    case (let controller as FriendsProfileViewController, let user as User):
        controller.user = user
    default:
        break
    }
}

Answer 2

我认为这个问题是我们总是从数组中取回一个Optional friends![indexPath.row]返回Optional(User)。

我最终将可选用户作为发件人传递。打开它并将其设置为我的其他VC。

override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
    performSegueWithIdentifier("viewFriend", sender: friends![indexPath.row])
}

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    print(sender)
    let destinationVC = segue.destinationViewController
    if let friendsProfileVC = destinationVC as? FriendsProfileViewController{
        if let friend = sender as? User{
            print(friend)
            print(friend.firstName)
            friendsProfileVC.user = friend
        }
    }
}

更新，我尝试将friendsProfileVC.user = friends?[indexPath.row]更改为friendsProfileVC.user = friends![indexPath.row]，但它确实有效。不知道为什么它早些时候不起作用。

使用Prepareforsegue将数据传递给被发现的控制器nil

2 个答案: