如何连续地将值从一个ViewController传递到第二个Viewcontroller并自动关闭，关闭第二个ViewController

Question

我尝试将数据从一个ViewController传递给secondControler，但是似乎不起作用。我使用NSNotification。 -2个控制器具有相同的类“ ViewController”

在viewcontroller.m

- (void)viewDidLoad {
       [super viewDidLoad];
       [[NSNotificationCenter defaultCenter] addObserver:self 
        selector:@selector(ProcessBarLoading) name:@"buttonPressed" object:nil];
   }
-(void)ProcessBarLoading{
      _labelTest.stringValue = @"TESTING";
    }
- (IBAction)test:(id)sender {
     [[NSNotificationCenter defaultCenter] postNotificationName:@"buttonPressed" object:self];
      NSStoryboard *storyboard = [NSStoryboard storyboardWithName:@"Main" bundle: nil];
      NSViewController * vc = [storyboard instantiateControllerWithIdentifier:@"SheetViewController"];    
[self presentViewControllerAsSheet:vc];
      }

运行程序并按按钮时，根本没有更新的标签文本。您知道为什么以及如何解决。

新代码： 在SecondViewController.m

@interface SencondViewController ()

@end

@implementation SencondViewController
@synthesize progressValue;
@synthesize labelView;
- (void)viewDidLoad {
 [super viewDidLoad];
 // Do view setup here.
 labelView.stringValue =progressValue;
 }

在FirstViewCOntroller中：

- (IBAction)test:(id)sender {
     self->uide = @"0";
     [self performSegueWithIdentifier:@"showRecipeDetail" sender:self->uide];
NSStoryboard *storyboard = [NSStoryboard storyboardWithName:@"Main" bundle: nil];

NSViewController * vc = [storyboard instantiateControllerWithIdentifier:@"SheetViewController"];
[self presentViewControllerAsSheet:vc];

- (void)prepareForSegue:(NSStoryboardSegue *)segue sender:(id)sender {
if ([segue.identifier isEqualToString:@"showRecipeDetail"]) {
SencondViewController * secondVC = segue.destinationController;
secondVC.progressValue = uide;
}  
}
- (IBAction)test2:(id)sender {

uide = @"80";
[self performSegueWithIdentifier:@"showRecipeDetail" sender:uide];
[self.view displayIfNeeded];
}

所以我是否同时按下按钮1（测试）和其他按钮2（测试2）始终显示具有更新值的新视图。我只需要显示1个视图。

Answer 1

为什么需要使用nsnotification，最简单的方法是使用prepareForSegue或委托

这是一个例子

    #pragma mark - Navigation

    // In a storyboard-based application, you will often want to do a little preparation before navigation
    - (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
        // Get the new view controller using [segue destinationViewController].
        // Pass the selected object to the new view controller.
        if ([segue.identifier isEqualToString:@"myId"]) {
            SecondViewController *vc = segue.destinationViewController;
            vc.myDataToPass = self.myValueInMyFirstViewController;
        }
}

Answer 2

  

不建议这样做的通知模式。使用通知   当您想将某些事件的数据传递给多个对象时。

要解决此问题：

步骤1：  您应该将View Controller名称更改为FirstViewController和SecondViewController，并在SecondViewController中声明一个属性，该属性要从FirstViewController设置。

步骤2： 最后，在FirstViewController的“准备Segue”方法中，设置数据。

在Objective-C中，您可以尝试以下代码：

#import "FirstViewController.h"
#import "SecondViewController.h"
@interface FirstViewController ()

@end

@implementation FirstViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

//This will trigger the prepareForSegue method

-(IBAction) someButtonClick {
    [self performSegueWithIdentifier:@"YourSequeId" sender:nil];
}


- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {

    SecondViewController * secondVC = segue.destinationViewController;
    secondVC.someValue = @"PassYourValueHere";

}



@end

，然后在SecondViewController的头文件中，声明属性：

#import <UIKit/UIKit.h>

@interface SecondViewController : UIViewController

@property (nonatomic,strong) NSString *someValue;

@end

在SecondViewController的实现文件中，编写：

#import "SecondViewController.h"

@interface SecondViewController ()

@property (nonatomic,weak) IBOutlet UITextField *yourTextField;
@end

@implementation SecondViewController

- (void)viewDidLoad {

    [super viewDidLoad];
    self.yourTextField.text = self.someValue

    // Do any additional setup after loading the view.
}



@end