NSNotificationCenter无法正常工作，如何调试

Question

我遵循dreammlax示例，但我似乎无法让我的NSNotification工作。是否需要添加框架或其他内容？我如何调试代码。

FirstViewController发布

#import "FirstViewController.h"

@interface FirstViewController ()

@end

@implementation FirstViewController

- (void)viewDidLoad {
    [super viewDidLoad];

}

- (IBAction)btnSend:(id)sender {

    [[NSNotificationCenter defaultCenter] postNotificationName:@"TestNotification" 
          object:self];

    self.tabBarController.selectedIndex = 1;

}

@end

SecondViewController接收

 #import "SecondViewController.h"

@interface SecondViewController ()

@end

@implementation SecondViewController

- (void)viewDidLoad {
    [super viewDidLoad];

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

   //===Removed ===[[NSNotificationCenter defaultCenter] removeObserver:self];

}

- (void) receiveTestNotification:(NSNotification *) notification
{

    if ([[notification name] isEqualToString:@"TestNotification"])
    NSLog (@"Successfully received the test notification!");

}

@end

Answer 1

添加观察者后删除[[NSNotificationCenter defaultCenter] removeObserver:self];，它将起作用

或者您可以将[[NSNotificationCenter defaultCenter] removeObserver:self];移至dealloc方法

- (void)dealloc {
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

关于第一次运行时无效的问题。

这是因为在初始化postNotificationName之前调用了SecondViewController。要解决此问题，请尝试以下代码。

- (IBAction)btnSend:(id)sender {
    self.tabBarController.selectedIndex = 1;

    [[NSNotificationCenter defaultCenter] postNotificationName:@"TestNotification" 
      object:self];
}

Answer 2

// from where u want to post notification  

- (IBAction)PressedMeBtn:(id)sender {

KNcreateOfferBack is define string!!!!

[[NSNotificationCenter defaultCenter] postNotificationName:KNcreateOfferBack object:nil];

}


//And where you are sending notification and observer 

- (void)BackFromControllers:(NSNotification *)note {
NSLog(@"Received Notification Inside LeftMenu - event");

if([[note name] isEqualToString:KNcreateOfferBack]){

    NSLog(@"KNcreateOfferBack NoteName :***: %@ :***:",note.name);
    // done your work here and then remove your notification !!!!
[[NSNotificationCenter defaultCenter] removeObserver:self name:KNcreateOfferBack object:nil];

 }

// use observer in viewWillAppear where you are using above method

 - (void)viewWillAppear:(BOOL)animated {


[super viewWillAppear:animated];
[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(BackFromControllers:)
                                             name:KNcreateOfferBack object:nil];
 }