I wrote code for iCloud key-value Store
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(keyValueStoreChanged:)
name:NSUbiquitousKeyValueStoreDidChangeExternallyNotification
object:nil];
LOG(#"sync");
[[NSUbiquitousKeyValueStore defaultStore] synchronize];
When I delete app and reinstall it, observer method is called usually, but sometimes not called.
Why? Just the network problem?
I had a similar issue where the NSUbiquitousKeyValueStoreDidChangeExternallyNotification wasn't triggering on the first launch after install, no matter how long I waited. Setting an initial key in the NSUBiquitousKeyValueStore seemed to solve this.
Immediately after adding the observer to the default store, I call:
[[NSUbiquitousKeyValueStore defaultStore] setString:#"testValue" forKey:#"testKey"];
[[NSUbiquitousKeyValueStore defaultStore] synchronize];
I use different keys (i.e. not testKey) for the actual data I want to sync.
Related
I have a method in a view controller that sets up some notifications:
- (void)processState
{
MYGame *game = [[MYGameManager sharedInstance] getGameAtIndex:self.indexPath.row];
if(game)
{
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(notification_gameUpdated:) name:kMYNotificationGameUpdated object:game];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(notification_gameEnded:) name:kMYNotificationGameEnded object:game];
}
}
Then there's a game updated method, which is called every so often:
- (void)notification_gameUpdated:(NSNotification *)notification
{
MYGame *game = notification.object;
_game_status = (game.entity.bet.isWinning) ? MYGameStatusWin : MYGameStatusLose;
}
And finally, when the game ends:
- (void)notification_gameEnded:(NSNotification *)notification
{
MYGame *game = notification.object;
// Clear the notifications
[[NSNotificationCenter defaultCenter] removeObserver:self name:kMYNotificationGameUpdated object:game];
[[NSNotificationCenter defaultCenter] removeObserver:self name:kMYNotificationGameEnded object:game];
self.gameIsActive = NO;
}
Trouble is, that even when I remove the observers (and a breakpoint shows that this is happening), then the notification_gameUpdated: method is still being called. If I change it to
[[NSNotificationCenter defaultCenter] removeObserver:self name:kMYNotificationGameUpdated object:nil];
This still won't clear it. But if I change it to
[[NSNotificationCenter defaultCenter] removeObserver:self name:nil object:game];
Then that does clear it. As does
[[NSNotificationCenter defaultCenter] removeObserver:self];
But I'm not keen on doing either, because I'd rather the code was clean and I don't want any "gotchas" further down the line if I need to add more observers. I've checked the rest of the code and cannot find any other classes adding observers to this object, although other view controllers do listen to the same messages.
Is processState called more than once? That would explain the behavior you are seeing.
If it is, one way to fix the issue would be to always remove listeners before adding them. See e.g. this answer.
edit #2
try registering with object:nil and when you post the notification include the reference to game in the userInfo dictionary. then, in the receiver, you can compare against game and perform whatever action you want if it is a match. this should get you the same behavior as if you were using object:game, although it does not explain why your current implementation isn't working
when you register for notifications like this:
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(notification_gameUpdated:)
name:kMYNotificationGameUpdated
object:game];
the #selector will only be performed if that particular instance of game is the sender.
is it possible that you're re-initializing your shared instance of game after registering? that could cause the behavior you're experiencing
try registering for notifications with object:nil and see what happens. (assuming there are not multiple games running concurrently)
So it turned out that the reason for the issue was Method Swizzling. The project I'm working on has addObserver:selector:name:object: and removeObserver:name:object: swizzled. The issue was that although addObserver has been handled correctly, removeObserver is only removing objects on specific conditions. This will obviously need to be changed...
But I post this as a warning to others... Swizzling can be dangerous to your health!
Apologies for any time wasted.
I use NSUserDefaults to save a switch on/off and so far it is good. It remembers the switch position in next session.
Now to the thing which I do not understand.
I use the same switch (with the same name)in another view, let´s say a flip view which is pushed in from the first view. If I change the switch in the first view it is automatically changed in the flip view.
But the other way round, if I change it in the flip view it is not changed in the first view when I go back. Only if I restart the application the first view is also changed.
How can I solve this to be changed at the same time? Or kind of refresh the first view without need to restart.
Your first view is not refreshed, as it is not initialized again. If you using ViewControllers you could update your switch in viewWillAppear (if isViewLoaded).
You should observe NSUserDefaults changes in views that are interested in the changes.
You can use the following code to observe the changes:
NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
[center addObserver:self
selector:#selector(defaultsChanged:)
name:NSUserDefaultsDidChangeNotification
object:nil];
And implement the defaultsChanged method:
- (void)defaultsChanged:(NSNotification *)notification
{
NSUserDefaults *defaults = (NSUserDefaults *)[notification object];
id value = [defaults objectForKey:#"keyOfDefaultThatChanged"];
self.something = [(NSNumber *)value intValue]; // For example.
}
Don't forget the remove the observer when your view closes (perhaps in dealloc):
NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
[center removeObserver:self];
I'm developing kind of a plugin for iTunes.
A lot of user have requested, that they would like to start the plugin if they start iTunes, which of course makes sense. However, I'm not sure how to do this.
I thought about a helper app, which is probably the only way.
The only thing that bothers me is how to get the notification.
Of course I could consistently check if iTunes is running, but I'm not sure if that's the right way to do it.
I would rather add my app as an observer of that process.
Is that possible?
If not, how does Activity Monitor do it?
SOLUTION
Thanks to Daij-Djan! I got it working like this:
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
[[[NSWorkspace sharedWorkspace] notificationCenter] addObserver:self
selector:#selector(iTunesLaunched:)
name:NSWorkspaceDidLaunchApplicationNotification
object:nil];
[[[NSWorkspace sharedWorkspace] notificationCenter] addObserver:self
selector:#selector(iTunesTerminated:)
name:NSWorkspaceDidTerminateApplicationNotification
object:nil];
}
-(void) iTunesLaunched:(NSNotification *)notification {
NSRunningApplication *runApp = [[notification userInfo] valueForKey:#"NSWorkspaceApplicationKey"];
if ([runApp.bundleIdentifier isEqualToString:#"com.apple.iTunes"])
NSLog(#"start");
}
-(void) iTunesTerminated:(NSNotification *)notification {
NSRunningApplication *runApp = [[notification userInfo] valueForKey:#"NSWorkspaceApplicationKey"];
if ([runApp.bundleIdentifier isEqualToString:#"com.apple.iTunes"])
NSLog(#"terminate");
}
register for NSWorkspace notifications:
NSWorkspaceDidLaunchApplicationNotification
NSWorkspaceDidTerminateApplicationNotification
see https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/ApplicationKit/Classes/NSWorkspace_Class/Reference/Reference.html
there is also the possibility to KVO the runningApplications property
btw cocoatech has a nice NTRunningAppManager class that does just that
So I'm new to NSNotifications, I am wondering what the scope is. I.e. If I have an Application Delegate Class, and it is the receiver of a notification:
-(id)init
{
[ super init];
if (!self) return nil;
// Add to our notification
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(receiveUpdateRequest:)
name:#"RequestStatusUpdate"
object:nil];
return self;
}
And has this method run on receive:
- (void) receiveUpdateRequest:(NSNotification *) notification
{
// Check the Notification Name
if ([[notification name] isEqualToString:#"RequestStatusUpdate"]){
NSLog (#"Recieved Update Status!");
}
else {
NSLog(#"Recieved Notification: %#",[notification name]);
}
}
Can I post a notification like so:
[[NSNotificationCenter defaultCenter] postNotificationName:#"RequestStatusUpdate" object:self];
From another object instance any where in my App?
Even for instance an object that instantiated by virtue of a NIB being loaded:
summaryWindow = [[SummaryWindowController alloc] initWithWindowNibName:#"SummaryWindow" owner:globalStatusController];
Do I have to have anything else configured in my summaryWindow Class to be able to call the postNotificationName method.
Or put a different way is the [NSNotificationCenter defaultCenter] global for all instances of all objects in my Application, I would assume thats how its suppose to work but currently when I call this method via an IBAction in my SummaryWindow , the notification does not seemed to be received.
I have tested both [NSThread currentThread] and the default Notification center and it does look like I'm in the thread and the same notification center ( which I think is always global). I am only looking into the thread thing as its come up on a few other threads.
2011-08-22 20:57:11.452 AppName[23102:1307] Using Default Notification Center: <CFNotificationCenter 0x10012c900 [0x7fff7d302ea0]>
2011-08-22 20:57:20.366 AppName[23102:1307] Using Default Notification Center: <CFNotificationCenter 0x10012c900 [0x7fff7d302ea0]>
Wow that was lame, I just found [[NSNotificationCenter defaultCenter] removeObserver:self]; in some earlier code. I had it in dealloc but some how managed to miss it in another NSTask method I was working on.
Or put a different way is the [NSNotificationCenter defaultCenter] global for all instances of all objects in my Application
Yes.
I would assume thats how its suppose to work but currently when I call this method via an IBAction in my SummaryWindow , the notification does not seemed to be received.
That's because you're registering in init. I'm betting this is Mac, and on Mac the application delegate is almost always instantiated from a nib file. You need to do this work in awakeFromNib.
Note that you generally do not need to check the notification's name. It's generally best to have a different method for each notification callback. You should also always create a string constant for your notification names. It's way too easy to mis-type them.
In there a way to do this? I register my object for UIPasteboardChangedNotification at launch time, but when sending it to the background and opening (for instance) Safari and copying some text, my handler never gets called.
(I'm using just the simulator for now).
I've used both:
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(pasteboardNotificationReceived:)
name:UIPasteboardChangedNotification
object:[UIPasteboard generalPasteboard]];
and:
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(pasteboardNotificationReceived:)
name:UIPasteboardChangedNotification
object:nil ];
to register my handler.
I had the same problem. According to the UIPasteboard Class Reference documentation for the changeCount property (emphasis is mine):
Whenever the contents of a pasteboard changes—specifically, when pasteboard items are added, modified, or removed—UIPasteboard increments the value of this property. After it increments the change count, UIPasteboard posts the notifications named UIPasteboardChangedNotification (for additions and modifications) and UIPasteboardRemovedNotification (for removals). ... The class also updates the change count when an application reactivates and another application has changed the pasteboard contents. When users restart a device, the change count is reset to zero.
I had read this to mean that my application would receive UIPasteboardChangedNotification notifications once my app was reactivated. A careful reading reveals, however, that it is only the changeCount that is updated when the app is reactivated.
I dealt with this by tracking the pasteboard's changeCount in my app delegate and posting the expected notification when I find the changeCount has been changed while the app was in the background.
In the app delegate's interface:
NSUInteger pasteboardChangeCount_;
And in the app delegate's implementation:
- (BOOL)application:(UIApplication*)application
didFinishLaunchingWithOptions:(NSDictionary*)launchOptions {
[[NSNotificationCenter defaultCenter]
addObserver:self
selector:#selector(pasteboardChangedNotification:)
name:UIPasteboardChangedNotification
object:[UIPasteboard generalPasteboard]];
[[NSNotificationCenter defaultCenter]
addObserver:self
selector:#selector(pasteboardChangedNotification:)
name:UIPasteboardRemovedNotification
object:[UIPasteboard generalPasteboard]];
...
}
- (void)pasteboardChangedNotification:(NSNotification*)notification {
pasteboardChangeCount_ = [UIPasteboard generalPasteboard].changeCount;
}
- (void)applicationDidBecomeActive:(UIApplication*)application {
if (pasteboardChangeCount_ != [UIPasteboard generalPasteboard].changeCount) {
[[NSNotificationCenter defaultCenter]
postNotificationName:UIPasteboardChangedNotification
object:[UIPasteboard generalPasteboard]];
}
}