Question

我有两个视图控制器，都在导航控制器内。父控制器是一个表视图，我为表视图正确设置了委托。当我在父视图控制器上点击一行时，我想要显示子控制器。这是有效的，即子视图控制器出现，我在子控制器上有一个“后退”导航按钮。

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    // Create and push another view controller.
    ChildVC *detailVC = [[ChildVC alloc] initWithNibName:@"ChildVC" bundle:nil];

    // When user dismisses child controller do this...
    [detailVC setDismissBlock:^{
        NSLog(@"Dismiss block called");
    }];

    // Setup navigation
    [self.navigationController pushViewController:detailVC animated:YES];
}

在ChildVC.h我有

@interface ChildVC : UIViewController
@property (nonatomic, copy) void (^dismissBlock)(void);
@end

在ChildVC.m中我有以下尝试执行父控制器的解除块代码，但无济于事，也就是说，我没有看到NSLog执行。

- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
    if (![[self.navigationController viewControllers] containsObject:self]) {
        // We were removed from the navigation controller's view controller stack
        // thus, we can infer that the back button was pressed
        **// How do I call the presenting controller's dissmissBlock?**
        **// I tried the following to no avail, since presentingViewController is nil**
        [[self presentingViewController] dismissViewControllerAnimated:YES completion:_dismissBlock];
    }
}

如果使用dismiss block不是这里的机制，那是什么？谢谢！

Answer 1

这是一种反模式，因为你的儿童视图控制器一般都不应该对他们的父母一无所知......但要解决你当前的问题 - 你在viewWillDisappear中调用dismiss块 - 并测试你的是否是你的视图控制器仍然在堆栈上将返回YES - 因为视图尚未消失。

另一个问题是'back'导航按钮，假设它是标准的UINavigationController后退按钮，已经调用了dismissViewControllerAnimated：方法，所以即使你把它改为viewDidDisappear，当你调用`[self presentingViewController]时“它将是零。

听起来你想做这样的事情：

- (void)viewDidDisappear:(BOOL)animated
{
    [super viewDidDisappear:animated];
    if (![[self.navigationController viewControllers] containsObject:self]) {
        if (_dismissBlock) _dismissBlock();
    }
}

如何在推送的视图控制器上调用dismissBlock属性？

1 个答案: