iphone - 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 View Controller 中调用以查看第二个 View Controller 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 可以将其自身设置为的委托(delegate)/协议(protocol)，那就更好了。您可以在这里找到更多信息Pass data back to the previous controller或者只是进行搜索。这种设计模式几乎在 iOS 编程中随处可见。

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”。