如何与不同的视图控制器通信？

Question

我有一个VC，它以模态方式呈现另一个VC。第二个VC推送到第三个VC。第三个VC解散自己，需要在初始VC上调用一个方法。我似乎无法让这个工作。有什么建议吗？

 VC3 *aVC3 = [[self.navigationController.viewControllers objectAtIndex:0] parentViewController];
 aVC3 = self.name;
 [aVC3 addExercise];
 [self dismissView];

Answer 1

delegate使用backward messsaging。

参考simple-delegate-tutorial-for-ios-development。另请参阅the-basics-of-protocols-and-delegates

如果你有UINavigationController，no need of delegate可以与navigationController中的任何viewController进行通信，如：

ViewController *objViewController = (ViewController *)[self.navigationController.viewControllers objectAtIndex:0]; //need to which controller u would like to communicate
[objViewController yourMethodHere]; // your method here

Answer 2

这是另一种方法：

第1步：在FirstViewController

中创建SecondViewController.h媒体资源

@interface SecondaryViewController : UIViewController{
}
@property (nonatomic, strong) FirstViewController *viewControllerOne;

第2步：在self

中展示SecondViewController时，将该属性设置为FirstViewController.m

@implementation SecondaryViewController

-(void)functionThatPresentsSecondViewController{
    SecondViewController *viewControllerTwo = [[SecondViewController alloc] init];
    [viewControllerTwo setViewControllerOne: self];
    [self presentViewController:viewControllerTwo animated:NO completion:nil];
}

第3步：您现在可以使用FirstViewController属性从SecondViewController调用viewControllerTwo.viewControllerOne个函数。