presentModalViewController 后如何访问 parentViewController？

Question

我需要在 presentMoalViewController 之后访问 parentViewController。 这是我在 firstViewController 中调用以查看 secondViewController 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];

}

当我点击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 可以将自己设置为的委托/协议会更好。您可以在这里找到更多信息Pass data back to the previous controller 或简单地进行搜索。这种设计模式在 iOS 编程中几乎无处不在。

最大的好处是，你的第二个 viewController 变得独立于任何呈现它的人，并且可以很容易地重用。技术术语是“解耦”。

Answer 2

我上次这样做时使用了通知：

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

在你的父 vc 视图中做：

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

Answer 3

对于navigationController，您可以声明一个类似于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];

在你的 parentViewController 类中你声明你的方法

- (void) saveData {

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

[self dismissModalViewControllerAnimated:YES];
}

然后您可以在您的navigationController 中调用[myController saveData]; 这应该有效，如果您有任何问题，请随时提问！

Answer 4

您可以使用以下方式访问您的父视图控制器-

- (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];

}