我有一个UICollectionView,当用户按下一个单元格时,我使用一个故事板以模态方式呈现UINavigationController中的另一个视图控制器.
- - (void)collectionView:(UICollectionView *)collectionView
- didSelectItemAtIndexPath:(NSIndexPath *)indexPath
- {
- [self performSegueWithIdentifier:@"editBookIPad"
- sender:indexPath];
- }
- - (void)prepareForSegue:(UIStoryboardSegue *)segue
- sender:(id)sender
- {
- // Did not include code for other segues,but I check which is the current one properly
- UINavigationController *dest = segue.destinationViewController; // This is nil!
- dest.modalPresentationStyle = UIModalPresentationFormSheet;
- DetailsViewController *detailsVC = (id)[dest topViewController];
- detailsVC.stack = self.stack;
- detailsVC.editingMode = 1;
- detailsVC.bookToEdit = [self.fetchedResultsController objectAtIndexPath:sender];
- [self.collectionView deselectItemAtIndexPath:sender
- animated:YES];
- }
现在,我的问题是segue.desinationViewController返回nil(如代码片段中的注释所示).
只是为了调试,我将UINavigationController更改为另一个视图控制器,我没有问题.我不知道是否从modal更改为push作为转换样式会有所帮助,因为它不可能推送UINavigationController(发生崩溃的情况就是这样).
我清理了项目和构建文件夹,然后重新启动了我的计算机(以及Xcode).
这是运行应用程序时的样子：
在寻找类似的问题时,我发现了这一点.大多数其他问题是关于在目标视图控制器上设置的属性为nil(例如this).
我使用Xcode 5.1.1并将iOS 7.0作为开发目标.
EDIT1
现在我的应用程序的所有部分都出现了同样的问题(UINavigationController以模态方式呈现).但是,它只在某些情况下发生,但每次segue.destinationViewController仍为零.
EDIT2
我用这个替换了prepareForSegue代码(手动完成)：
- UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Storyboard"
- bundle:nil];
- UINavigationController *navCon = [storyboard instantiateViewControllerWithIdentifier:@"AllBooksVCDetails"]; // The problematic navigation controller
- navCon.modalPresentationStyle = UIModalPresentationFormSheet;
- BKSBookDetailsViewController *detailsVC = (id)[navCon topViewController];
- detailsVC.stack = self.stack;
- detailsVC.editingMode = 1;
- detailsVC.bookToEdit = [self.fetchedResultsController objectAtIndexPath:indexPath];
- [self presentViewController:navCon
- animated:YES
- completion:nil];
- [self.collectionView deselectItemAtIndexPath:indexPath
- animated:YES];
这很有效.所以我认为问题出在故事板上.
解决方法
将tracecontroller嵌入到NavigationController中时遇到了同样的问题.
- override public func prepareForSegue(segue: UIStoryboardSegue,sender: AnyObject?) {
- let destinationVC = segue.destinationViewController as! UINavigationController
- let nextViewController = destinationVC.viewControllers[0] as! SecondViewController
- nextViewController.someProperty = someValue
- }
这个链接帮助我：
