ios - 如果更改了呈现 View Controller ，如何关闭模态视图 Controller ？

Question

我在 iPad 上展示模态视图 Controller ，它会在展示时更改展示 View Controller 。例如:

1. 当用户在 TableView 中选择一个单元格时， View Controller VC 会呈现模态视图 Controller 。
2. 用户在模态视图 Controller 上选择一个项目，然后打开另一个 VC 实例来代替第一个。重要的是，替换第一个的 View Controller 实例属于同一类型。
3. 模态视图 Controller 无法关闭或发生 EXC_BAD_ACCESS 异常。

失败的解除是可以理解的:呈现 View Controller 不再可用。基本上，我如何从不同的呈现 View Controller 中关闭这个呈现的模态视图 Controller ？

我已有的代码是:

ViewController1.m

- (void)showModalViewController:(UIViewController *)viewController
{
    UINavigationController *navigationController = [[UINavigationController alloc] initWithRootViewController:viewController];
    navigationController.modalPresentationStyle = UIModalPresentationFormSheet;
    viewController.navigationItem.rightBarButton = [[UIBarButton alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemDone target:self action:@selector(dismissModalViewController)];
    [self presentViewController:navigationController animated:YES completion:nil];
}

- (void)dismissModalViewController
{
    [self dismissViewControllerAnimated:YES completion:nil];
    [self.tableView deselectRowAtIndexPath:[self.tableView indexPathForSelectedRow] animated:YES];
}

Answer 1

感谢您的建议，但我通过使用委托(delegate)解决了这个问题。呈现的 View Controller 定义了一个委托(delegate)，用于在发生操作时通知呈现器。

ChildViewControler.h:

@protocol ChildViewControllerDelegate <NSObject>
- (void) childView:(ChildViewController *)childView didSelectItem:(Item *)item;
@end

ChildViewController.m:

// in interface
@property (nonatomic, weak) id <ChildViewControllerDelegate> delegate;

// in implementation
- (void)closeView:(Item *)anItem
{
    [self.delegate childView:self didSelectItem:anItem];
}

ViewController1.m:

- (void)showModalViewController:(UIViewController *)viewController
{
    UINavigationController *navigationController = [[UINavigationController alloc] initWithRootViewController:viewController];
    navigationController.modalPresentationStyle = UIModalPresentationFormSheet;
    viewController.navigationItem.rightBarButton = [[UIBarButton alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemDone target:self action:@selector(dismissModalViewController)];
    // Different view controller types may be passed here so check is required...
    if (viewController.class == [ChildViewController class]) {
        ((ChildViewController *)viewController).delegate = self;
    [self presentViewController:navigationController animated:YES completion:nil];
}

- (void)childView:(ChildViewController *)childView didSelectItem:(Item *)item
{
    [self dismissViewControllerAnimated:YES completion:nil];
    [self.tableView deselectRowAtIndexPath:[self.tableView indexPathForSelectedRow] animated:YES];
    // Perform action required with 'item'
}