PresentModalViewController之后如何访问parentViewController？

Question

我需要在presentMoalViewController 之后访问parentViewController。 这是我在第一个视图控制器中调用以查看第二个视图控制器的方法：

- (void)viewData {

    SecondViewController *viewCtrl = [self.storyboard instantiateViewControllerWithIdentifier:@"select_data"];
    UINavigationController *navigationController = [[UINavigationController alloc] initWithRootViewController:viewCtrl];
    navigationController.navigationBar.barStyle = UIBarStyleBlack;

    UIBarButtonItem *saveButton = [[[UIBarButtonItem alloc] initWithTitle:@"Save" style:UIBarButtonItemStyleDone target:viewCtrl action:@selector(saveData)] autorelease];
    viewCtrl.navigationItem.rightBarButtonItem = salvaButton;

    UIBarButtonItem *undoButton = [[[UIBarButtonItem alloc] initWithTitle:@"Undo" style:UIBarButtonItemStyleBordered target:viewCtrl action:@selector(backView)] autorelease];
    viewCtrl.navigationItem.leftBarButtonItem = annullaButton;

    [self presentModalViewController:navigationController animated:YES];

}

当我单击 saveButton 时，我尝试以这种方式访问​​parentViewController，但它不起作用：

- (void) saveData {

    FirstViewController *parentView = (FirstViewController*)[[self navigationController] presentingViewController];
    parentView.dataString = [[NSMutableString alloc] initWithFormat:@"new string"];
    [parentView performSelectorInBackground:@selector(myMethod) withObject:nil];

    [self dismissModalViewControllerAnimated:YES];

}

Answer 1

如果您在第二个 viewController 中使用第一个 viewController 可以将其自身设置为的委托/协议，那就更好了。您可以在此处将数据传回之前的控制器或简单地进行搜索来找到更多信息。这种设计模式几乎在 iOS 编程中无处不在。

最大的优点是，你的第二个 viewController 变得独立于呈现它的人，并且可以轻松地重用。技术术语是“脱钩”。

Answer 2

上次我这样做时，我使用了 notification:

[[NSNotificationCenter defaultCenter] postNotificationName:@"saveData" object:dataString];

在你的父 vc 视图中 didload:

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(saveDataNow:) name:@"saveData" object:nil];

Answer 3

对于 navigationController，您可以声明一个名为 myController 的属性，然后您必须像这样启动您的 navigationController：

UINavigationController *navigationController = [[UINavigationController alloc] initWithRootViewController:viewCtrl];
navigationController.navigationBar.barStyle = UIBarStyleBlack;
navigationController.myController = self;

UIBarButtonItem *saveButton = [[[UIBarButtonItem alloc] initWithTitle:@"Save" style:UIBarButtonItemStyleDone target:viewCtrl action:@selector(saveData)] autorelease];
viewCtrl.navigationItem.rightBarButtonItem = salvaButton;

UIBarButtonItem *undoButton = [[[UIBarButtonItem alloc] initWithTitle:@"Undo" style:UIBarButtonItemStyleBordered target:viewCtrl action:@selector(backView)] autorelease];
viewCtrl.navigationItem.leftBarButtonItem = annullaButton;

[self presentModalViewController:navigationController animated:YES];

在您的 parentViewController< /code> 您声明方法的类

- (void) saveData {

FirstViewController *parentView = (FirstViewController*)[[self navigationController] presentingViewController];
parentView.dataString = [[NSMutableString alloc] initWithFormat:@"new string"];
[parentView performSelectorInBackground:@selector(myMethod) withObject:nil];

[self dismissModalViewControllerAnimated:YES];
}

在您的 navigationController 中，您可以调用 [myController saveData];
这应该有效，如果您有任何疑问，请随时询问！

Answer 4

您可以使用以下方式访问父视图控制器 -

- (void) saveData {
NSMutableArray *activeControllerArray = [self.navigationController.viewControllers mutableCopy];
FirstViewController *parentView;
for(int i = 0, i <[activeControllerArray  count], i++) {
    if([[activeControllerArray objectAtIndex:i] isKindOfClass:[FirstViewController class]) {
        parentView= [activeViewController objectAtIndex:i];
        break;
     }
}

parentView.dataString = [[NSMutableString alloc] initWithFormat:@"new string"];
[parentView performSelectorInBackground:@selector(myMethod) withObject:nil];

[self dismissModalViewControllerAnimated:YES];

}