I am using NSNotification to pass value between ViewControllers, but value is not getting passed and when i used breakpoints to check what's going wrong i came to know that the receive notification selector method is not called.
Following is the code what i have written
AViewController.m
[[NSNotificationCenter defaultCenter] postNotificationName:#"speciality" object:nil userInfo:[specialityIdArray objectAtIndex:indexPath.row]];
BViewCOntroller.m
-(void)viewWillAppear:(BOOL)animated
{
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(receiveSpecialityId:) name:#"speciality" object:nil];
}
-(void)receiveSpecialityId:(NSNotification *)notificaton
{
NSString *selectedServiceString=[[notificaton userInfo] valueForKey:#"service"];
_specialtiyId = selectedServiceString;
[[NSNotificationCenter defaultCenter] removeObserver:self name:#"service" object:nil ];
}
I am trying to pass value from AViewController to BViewController
I have read all the discussions done previously on this same issue, but none of them solved my issue
Dont' add
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(receiveSpecialityId:) name:#"speciality" object:nil];
in the viewDidAppear. I don't know much objective c but here's the deal in swift:
func receiveSpecialityID(notification: NSNotification){
NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(<Theclassinwhichthismethodiswritten without the ()).receiveSpecialityID(_:)), name: "Selected", object: nil)
/// DO your thing here..
}
Then do a:
deinit{
NSNotificationCenter.DefaultCenter().removeObserver
}
This should work. Try and let me know!
Related
This is my code.
Here create the observer to Notification called Example into ViewController
- (void)addObserverExample
{
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(example:)
name:#"Example"
object:nil];
}
- (void)example:(NSNotification *)notification{
NSLog(#"Example!!!");
}
From viewDidLoad register my observer
- (void)viewDidLoad
{
[self addObserverExample];
}
In my second ViewController. When tapped a button excute this code:
[[NSNotificationCenter defaultCenter] postNotificationName:#"Example" object:self.dictKeys userInfo:nil];
The problem I have is that the notification is never executed.
Any idea.
Have created demo for NSNotificationCenter as per your question and it's working fine for me. Here it is the link of that code: NSNotificationCenter Demo
- (void)viewDidLoad {
[super viewDidLoad];
[self addObserverExample];
}
- (void)addObserverExample
{
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(example:)
name:#"Example"
object:nil];
}
- (void)example:(NSNotification *)notification{
NSLog(#"Example!!!");
NSLog(#"%#",notification.userInfo);
}
- (IBAction)btnFireNotification:(id)sender {
[[NSNotificationCenter defaultCenter] postNotificationName:#"Example" object:nil userInfo:#{#"key" : #"value"}];
}
I believe the problem you're having may be related to the fact that in your second view controller, you're passing self.dictKeys in the object parameter.
If you want to pass data via the NSNotificationCenter, you should use the userInfo parameter instead.
Darshan's example does this the correct way.
In my custom UITableViewCell I added an observer in NSNotificationCenter:
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(stopActivityIndicator) name:#"stopActivityIndicator" object:nil];
I post a notification in a UIViewController:
[[NSNotificationCenter defaultCenter] postNotificationName:#"stopActivityIndicator" object:nil];
This function "stopActivityIndicator" is not being called, any idea what causes this?
EDIT:
ExploreViewController.m
-(void)showCorrectBannerAfterPlusButtonClicked:(NSNotification *)notification
{
[[NSNotificationCenter defaultCenter] postNotificationName:#"stopActivityIndicator" object:nil];
}
ExploreViewController contains a UITableView with ExploreTableViewCells.
ExploreTableViewCell.m
- (IBAction)plusButtonClicked:(id)sender
{
self.plusButton.hidden = YES;
[self.plusButtonActivityIndicator startAnimating];
[[NSNotificationCenter defaultCenter]addObserver:self selector:#selector(stopActivityIndicator) name:#"stopActivityIndicator" object:nil];
}
-(void)stopActivityIndicator
{
_plusButton.hidden = NO;
[self.plusButtonActivityIndicator stopAnimating];
[[NSNotificationCenter defaultCenter]removeObserver:self name:#"stopActivityIndicator" object:nil];
}
Ok, question, when do you call "showCorrectBannerAfterPlusButtonClicked"?? As this is the method where you post the notification observed by the tableViewCell.
What I see is the notification observer adding and removal, but I don't see how the UIViewController knows when the cell's "plusButtonClicked" is called, so perhaps the method posting the notification is not being called.
Also, be careful with the cell reusage, have in mind if you should remove the observer at that point.
Below is what I have.
MainViewController.m
- (IBAction)sideMenuAction:(id)sender {
NSLog(#"login==sideMenuAction");
[[NSNotificationCenter defaultCenter] postNotificationName:#"ShowMySideMenuNotification" object:self];
}
NotificationListener.m
-(void)viewDidLoad {
[[NSNotificationCenter defaultCenter] removeObserver:self name:#"ShowMySideMenuNotification" object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(adjustShowMenu) name:#"ShowMySideMenuNotification" object:nil];
}
-(void) adjustShowMenu {
NSLog(#"notification adjustShowMenu=");
}
Now when I click side menu button in MainViewController, what I was expecting is call adjustShowMenu from NotificationListener once, however it is called twice.
Below is the NSLog for the same.
2015-01-20 12:27:30.798 abc[699:169314] login==sideMenuAction
2015-01-20 12:27:30.798 abc[699:169314] notification adjustShowMenu=
2015-01-20 12:27:30.799 abc[699:169314] notification adjustShowMenu=
What I was expecting is
2015-01-20 12:27:30.798 abc[699:169314] login==sideMenuAction
2015-01-20 12:27:30.798 abc[699:169314] notification adjustShowMenu=
Any idea what is going wrong?
Note: I also tried in viewDidAppear instead of viewDidLoad, but its giving same result.
When I searched online, many answers asked to removeObserver. I did same, but still twice notification is getting called.
As per answer here, I make changes as below and its working fine now.
-(void) viewWillAppear:(BOOL)animated {
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(adjustShowMenu) name:#"ShowMySideMenuNotification" object:nil];
}
-(void) viewWillDisappear:(BOOL)animated {
[[NSNotificationCenter defaultCenter] removeObserver:self name:#"ShowMySideMenuNotification" object:nil];
}
Hi i am trying to use NSNotification center in my application.The selector method is not being called from the code.I found similar questions in this site like this, but still i am unable to resolve the error.
i am posting notification in appdelegate did finish launching as:
[[NSNotificationCenter defaultCenter] postNotificationName:#"ualert" object:self userInfo:userDict];
adding an observer in one of the view controller as:
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(remoteNotificationReceived:)
name:#"ualert"
object:nil];
my selector method is:
- (void)remoteNotificationReceived:(NSNotification *)notification
{
NSLog(#"Notification: %#", notification.userInfo);
}
removing observer as:
- (void)dealloc
{
[[NSNotificationCenter defaultCenter] removeObserver:self];
}
You are posting ualert in applicationDidFinishLaunching which will necessarily occur before your view controller is loaded (and therefore before you have added the observer for the notification).
A UIViewController adds itself to the default center:
[[NSNotificationCenter defaultCenter]
addObserver:self
selector:#selector(editFood)
name:#"editFood"
object:nil];
Then a UITableView delegate NSObject posts a NSNotification:
[[NSNotificationCenter defaultCenter]
postNotificationName:#"editFood"
object:self];
During run time it get a EXC_BAD_ACCESS exception.
Is the defaultCenter getting released somewhere? The same concept works when I post a notification to a UIViewController from a UIViewController, but that shouldn't matter, right?
One of your subscribers has been deallocated. Make sure to call [[NSNotificationCenter defaultCenter] removeObserver:self] in your dealloc (if not sooner).
EXC_BAD_ACCESS can happen even after verifying dealloc exists like so:
- (void)dealloc {
[[NSNotificationCenter defaultCenter] removeObserver:self]
}
The above will solve the problem most of the time, but apparently my cause was that I was indirectly adding the observer with a selector: set to nil as follows:
[NSNotificationCenter.defaultCenter addObserver:self
selector:nil
name:notificationName
object:nil];
...so when I posted something with that notificationName, EXC_BAD_ACCESS occurred.
The solution was to send a selector that actually points to something.
I had the same issue in Swift. The problem was the function target had a closure parameter with default value:
#objc func performFoo(completion: (() -> Void)? = nil) {
...
}
After I replace the closure parameter with a Notification parameter, it worked:
#objc func performFoo(notification: Notification) {
...
}
I had to make some refactor to make it works in a right way.