Ios dismissModalViewController 并传回数据

你需要使用委托协议...以下是如何做到这一点:

在secondViewController的头文件中声明协议.应该是这样的:

#import <UIKit/UIKit.h>

@protocol SecondDelegate <NSObject>
-(void)secondViewControllerDismissed:(NSString *)stringForFirst
@end


@interface SecondViewController : UIViewController
{
    id myDelegate;  
}

@property (nonatomic, assign) id<SecondDelegate>    myDelegate;

不要忘记在实现(SecondViewController.m)文件中合成myDelegate:

@synthesize myDelegate;

在FirstViewController的头文件中，通过以下操作订阅Second Delegate协议:

#import "SecondViewController.h"

@interface FirstViewController:UIViewController <SecondDelegate>

现在，当您在FirstViewController中实例化SecondViewController时，您应该执行以下操作:

// If you're using a view controller built with Interface Builder.
SecondViewController *second = [[SecondViewController alloc] initWithNibName:"SecondViewController" bundle:[NSBundle mainBundle]];
// If you're using a view controller built programmatically.
SecondViewController *second = [SecondViewController new]; // Convenience initializer that uses alloc] init]
second.myString = @"This text is passed from firstViewController!";
second.myDelegate = self;
second.modalTransitionStyle = UIModalTransitionStyleCrossDissolve;
[self presentModalViewController:second animated:YES];
[second release];

最后，在第一个视图控制器的实现文件(FirstViewController.m)中，为secondViewControllerDismissed实现SecondDelegate的方法:

- (void)secondViewControllerDismissed:(NSString *)stringForFirst
{
    NSString *thisIsTheDesiredString = stringForFirst; //And there you have it.....
}

现在，当您要取消第二个视图控制器时，您希望调用在第一个视图控制器中实现的方法.这部分很简单.您所要做的就是在第二个视图控制器中，在解除代码之前添加一些代码:

if([self.myDelegate respondsToSelector:@selector(secondViewControllerDismissed:)])
{
    [self.myDelegate secondViewControllerDismissed:@"THIS IS THE STRING TO SEND!!!"];
}
[self dismissModalViewControllerAnimated:YES];

委托协议非常、非常、非常有用.熟悉一下它们会对你有好处:)

NSNotification是实现此目的的另一种方式，但作为最佳实践，当我希望跨多个viewController或对象进行通信时，我更喜欢使用它.如果你对使用NSNotitification感兴趣，这是我在早些时候发布的一个答案:Firing events accross multiple viewcontrollers from a thread in the appdelegate

编辑:

如果要传递多个参数，则解除之前的代码如下所示:

if([self.myDelegate respondsToSelector:@selector(secondViewControllerDismissed:argument2:argument3:)])
{
    [self.myDelegate secondViewControllerDismissed:@"THIS IS THE STRING TO SEND!!!" argument2:someObject argument3:anotherObject];
}
[self dismissModalViewControllerAnimated:YES];

这意味着您的firstViewController内的Second Delegate方法实现现在将如下所示:

- (void) secondViewControllerDismissed:(NSString*)stringForFirst argument2:(NSObject*)inObject1 argument3:(NSObject*)inObject2
{
    NSString thisIsTheDesiredString = stringForFirst;
    NSObject desiredObject1 = inObject1;
    //....and so on
}