ios - 在dismissViewController回调中刷新presentingViewController的UI时意外发现nil

Question

我正在尝试重新加载呈现另一个 View (BuyView) 的 View (MyMatches) 的 UI。当 BuyView 被关闭时，我想重新加载 MyMatches 的所有 View 。然而，当我尝试在“dismissViewController”完成时执行此操作时，我在“let mmvc = self.presentingViewController？as!MyMatchesViewController”行上遇到了“意外发现nil”错误。有谁知道为什么会发生这种情况，或者是否有更简单的方法来完成我想做的事情？下面发布的代码可在 BuyViewController 中找到:

func itemBought() {
    print("Confirm tapped!")
    BoughtController.globalController.sendSellerNotification(seller, match: match)
    BoughtController.globalController.updateBuyer(self.item, buyer: LocalUser.user, match: self.match)
    BoughtController.globalController.updateMarket(self.item, match: self.match)
    BoughtController.globalController.updateSeller(self.item, seller: seller, soldPrice: self.match.matchedPrice)


    self.cancel = false

    if self.fromInfo == true {

        self.presentingViewController?.dismissViewControllerAnimated(true, completion: nil)
    }


    else {
        self.dismissViewControllerAnimated(true) {
            let mmvc = self.presentingViewController as! MyMatchesViewController
            mmvc.setupMatchesScrollContent()
        }
    }

}

Answer 1

很可能，dismissViewControllerAnimated() block 在 View Controller 被关闭后运行，因此 self.presentingViewController 发生了变化？也许。使用更安全:

else {
   let mmvc = self.presentingViewController as! MyMatchesViewController              
   self.dismissViewControllerAnimated(true) {
     mmvc.setupMatchesScrollContent()
   }
}

在尾随闭包中使用 mmvc 之前“捕获”它的位置。