Update UI from another class - ios

I am trying to separate my GUI and my Logic...For example, i have one class which calculates something (calc.h/calc.m). And i have my GUI (viewController.h/viewController.m)...Now i want to update one Element of the GUI from another class... I already tried it with a Singleton, like this:
calc.m:
viewController *con = [viewController sharedInstance];
con.download.text = #"It Works";
viewController.m:
+ (id)sharedInstance {
static id sharedInstance;
#synchronized(self) {
if (!sharedInstance)
sharedInstance = [[viewController alloc] init];
return sharedInstance;
}
}
But it does´t work...
UPDATE:
in my ViewController:
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(receiveNotification:)
name:#"UpdateDownloadLabel"
object:nil];
- (void) receiveNotification:(NSNotification *) notification
{
NSDictionary* userInfo = notification.userInfo;
if ([[notification name] isEqualToString:#"Update"])
{
download.text = [userInfo valueForKey:#"Test"];
}
}
And in my other class i post the notification like this:
[[NSNotificationCenter defaultCenter]
postNotificationName:#"UpdateDownloadLabel"
object:nil userInfo:info];
But it doesn't work...

That's not a proper use of a singleton. If you need to notify your UI from your model you have these options:
- delegation
- Local Notification
- KVO
The general rule is to keep your logic decoupled from your presentation, therefore your calc class shouldn't really know that a label named download exists.

Example: How to use notification.
In classA.h file
extern NSString * const ClassADidViewNotification;
In classA.m file
NSString * const ClassADidViewNotification = #"ClassADidViewNotification";
Register for notification in classA.m :-
NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
[center addObserverForName: XXFooDidBarNotification
object:nil
queue:nil
usingBlock:^(NSNotification *notification)
{
NSLog(#"notification.object: %#", notification.object);
}
];
Post Notification:-
ClassB.m
[[NSNotificationCenter defaultCenter] postNotificationName: ClassADidViewNotification object:nil];

Related

postNotificationName is not yet trigger in appdelegate class

In Appdelegate.m added postNotification method
- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo {
if(application.applicationState == UIApplicationStateBackground) {
[[NSNotificationCenter defaultCenter] postNotificationName: #"SuggetionPushNotification" object:nil userInfo:userInfo];
AppDelegate *appDel = (AppDelegate *)[[UIApplication sharedApplication] delegate];
SideMenuViewController *leftMenuViewController = [[SideMenuViewController alloc] init];
MFSideMenuContainerViewController *container = [MFSideMenuContainerViewController
containerWithCenterViewController:[[UINavigationController alloc]
initWithRootViewController:[[SuggetionViewController alloc] init]]
leftMenuViewController:leftMenuViewController
rightMenuViewController:Nil];
[self.window makeKeyAndVisible];
appDel.window.rootViewController = container;
}
}
ViewController B (SuggetionViewController) In viewDidLoad
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(receiveTestNotification:)
name:#"SuggetionPushNotification"
object:nil];
- (void) receiveTestNotification:(NSNotification *) notification {
NSLog(#"working");
}
But here not yet fire Notification, if added both post and addobserver in same class then only it fire. what wrong i made. I referred from Send and receive messages through NSNotificationCenter in Objective-C? Please help
Your View Controller B is not in memory when you are posting the notification thats why Controller B is unable to observe the notification. Add Delay before posting the notification will help.
double delayInSeconds = 2.0;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC));
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
[[NSNotificationCenter defaultCenter] postNotificationName: #"SuggetionPushNotification" object:nil userInfo:nil];
});
You're calling your notification from the launch method in the app delegate before any view/viewcontroller hierarchy has a change to instantiate and load. The reason you are not getting the notification is because your SuggetionViewController has not been instantiated yet. If you want the notification to be received, you need to fire it after the view controller gets a change to be created.
You can't receive notification inside your SuggetionViewController if it's now loaded.
You add the observer in the viewDidLoad so it can happens that you recieve a remote notification while the SuggetionViewController is not loaded.
You should ensure that your controller is loaded before processing notifications.
In your AppDelegate implementation add this
static void displayStatusChanged(CFNotificationCenterRef center, void *observer,
CFStringRef name, const void *object,
CFDictionaryRef userInfo) {
if (name == CFSTR("com.apple.springboard.lockcomplete")) {
[[NSUserDefaults standardUserDefaults] setBool:YES
forKey:#"kDisplayStatusLocked"];
[[NSUserDefaults standardUserDefaults] synchronize];
}
}
In applicationDidFinishLaunchingWithOptions, add this below code
CFNotificationCenterAddObserver(
CFNotificationCenterGetDarwinNotifyCenter(), NULL, displayStatusChanged,
CFSTR("com.apple.springboard.lockcomplete"), NULL,
CFNotificationSuspensionBehaviorDeliverImmediately);
Post it in your didRecieveRemoteNotification method.
[[NSNotificationCenter defaultCenter]postNotificationName:#"TestNotification" object:self];
Post this in your view controller viewDidLoad method.
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(receiveTestNotification:)
name:#"TestNotification"
object:nil];
Then it will trigger this method.
- (void) receiveTestNotification:(NSNotification *) notification
{
if ([[notification name] isEqualToString:#"TestNotification"]) {
NSLog (#"Successfully received the test notification!");
}
}
Your 'SuggetionViewController' object is not initialized when you post the notification. So there is no 'SuggetionViewController' object to catch the notification.
- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo{
if(application.applicationState == UIApplicationStateBackground) {
AppDelegate *appDel = (AppDelegate *)[[UIApplication sharedApplication] delegate];
SideMenuViewController *leftMenuViewController = [[SideMenuViewController alloc] init];
SuggetionViewController *sug_controller = [[SuggetionViewController alloc] init]];
[sug_controller registerNotification];
[[NSNotificationCenter defaultCenter] postNotificationName: #"SuggetionPushNotification" object:nil userInfo:userInfo];
MFSideMenuContainerViewController *container = [MFSideMenuContainerViewController containerWithCenterViewController:[[UINavigationController alloc] initWithRootViewController:sug_controller leftMenuViewController:leftMenuViewController rightMenuViewController:Nil];
[self.window makeKeyAndVisible];
appDel.window.rootViewController = container;
}
}
Add the following instance method to SuggetionViewController
- (void)registerNotification
{
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(receiveTestNotification:) name:#"SuggetionPushNotification" object:nil];
}
- (void)receiveTestNotification
{
NSlog(#"Notification recieved-->>>");
}

How to Show Push Notifications on another ViewController. I am receiveing it on Appdelegate page on all the three cases

Please tell me how to send the appdelegate to another viewcontroller using NSdoctionary and receive it on the new view controller and show it.
-(void)application:(UIApplication*)application didReceiveRemoteNotification: (NSDictionary*)userInfo
{
NSLog(#"Push received: %#", userInfo);
}
There are few ways/ But I prefer using https://developer.apple.com/library/ios/documentation/Cocoa/Reference/Foundation/Classes/NSNotificationCenter_Class/index.html
Somrewere in constants
NSString *const NOTIFICATION_ID = #"com.yourapp.notificationID";
ViewController.m
- (void)viewDidLoad
{
NSNotificationCenter * notificationCenter = [NSNotificationCenter defaultCenter];
[notificationCenter addObserver:self
selector:#selector(notificationRecieved:)
name:NOTIFICATION_ID
object:nil];
}
- (void)notificationRecieved:(NSNotification*)notification
{
NSLog(#"Push received: %#", notification.userInfo);
}
- (void)dealloc
{
[[NSNotificationCenter defaultCenter] removeObserver:self name:NOTIFICATION_ID object:nil];
}
AppDelegate.m
-(void)application:(UIApplication*)application didReceiveRemoteNotification: (NSDictionary*)userInfo
{
[[NSNotificationCenter defaultCenter] postNotificationName:NOTIFICATION_ID object:nil userInfo:userInfo];
}
Use Notifications. The app delegate will post the notification with the notification dictionary, the view controller will be listening for it.

NSNotification postNotification and addObserver

I am trying to do a notification from a location manager object to my viewController. It's not working - the selector in the addObserver method doesn't get called.
Location Manager Object.m files (singleton with standard dispatch once & init methods)
- (void)setCurrentLocation:(CLLocation *)currentLocation
{
if (!_location) {
_location = [[CLLocation alloc] init];
}
_location = currentLocation;
NSNumber *latitude = [NSNumber numberWithDouble:self.location.coordinate.latitude];
NSNumber *longitude = [NSNumber numberWithDouble:self.location.coordinate.longitude];
NSLog(#"lat %# & long %# in notification section", latitude, longitude);
NSNotification *notification = [NSNotification notificationWithName:#"myNotification" object:self userInfo: #{kSetLat: latitude,
kSetLong: longitude}];
[[NSNotificationCenter defaultCenter] postNotification:notification];
}
ViewController.m (garden variety)
- (IBAction)welcomeNotification:(UIButton *)sender {
NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
[center addObserver:self selector:#selector(sendGetRequest:) name:#"myNotification" object:[LPLocationManager sharedManager]];
[center removeObserver:self];
NSLog(#"welcomeNotication triggered");
}
The way you do is not correct. Why you add the observer and then remove it immediately. Most of the time, we add/remove observer in viewWillAppear and viewWillDisappear or viewDidAppear and viewDidDisappear.
It should be something like:-
-(void)viewWillAppear:(BOOL)animated{
[super viewWillAppear:animated];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(sendGetRequest:) name:#"myNotification" object:nil];
}
-(void)viewWillDisappear:(BOOL)animated{
[super viewWillDisappear:animated];
[[NSNotificationCenter defaultCenter] removeObserver:self name:#"myNotification" object:nil];
}

Where is the best place to remove Observer from Notification Center

I think that should be here:
-(void) viewWillDisappear:(BOOL)animated
{
[super viewDidDisappear:animated];
NSNotificationCenter *nc = [NSNotificationCenter defaultCenter];
[nc removeObserver:self];
}
or maybe in -dealloc.
Both sound strange to me so I´m not totally sure of it.
First, in my AppDelegate I´m listening to a Remote Notification Via Parse
- (void)application:(UIApplication *)application
didReceiveRemoteNotification:(NSDictionary *)userInfo {
[PFPush handlePush:userInfo];
NSString * urlToGo = [userInfo objectForKey:#"url"];
NSLog (#"Recibo notificación con paremetro url: %#", urlToGo);
NSNotification *note = [NSNotification
notificationWithName:PUSH_NOTIFICATION
object:self
userInfo:userInfo];
[[NSNotificationCenter defaultCenter] postNotification:note];
}
and in myViewController
- (void) viewDidLoad {
[super viewDidLoad];
_lastMenuSelected=menu1;
NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
NSOperationQueue *mainQueue = [NSOperationQueue mainQueue];
[center addObserverForName:PUSH_NOTIFICATION
object:nil
queue:mainQueue
usingBlock:^(NSNotification *note) {
// Save in property to load parameter in prepareForSegure
_urlToLoadFromPush = urlToGoReceivedFromPush;
[self showPush:self];
}];
}
- (void)showPush:(id)sender {
PushViewController * pushViewController=(PushViewController*)[self.storyboard instantiateViewControllerWithIdentifier:#"PushId"];
pushViewController.url = _urlToLoadFromPush;
UINavigationController* nVC=[[UINavigationController alloc] initWithRootViewController:pushViewController];
[self presentViewController:nVC animated:YES completion:^{
//[_delegate logout];
}];
}
Since you seem to be adding the observer in the viewDidLoad method (which is only called once as of iOS 6), you should remove the observer in the dealloc method.
Don't remove the observer in viewWillDisappear beacause generally we require to post the notification when the view is in the stack but not appearing. So always try to remove the observers in -(void)dealloc with the name of observer.

Unable to receive notification

I try to send local notification. Here some code for class sending the notification:
#interface Sender : UIView
{
NSInteger itemID;
}
#implementation Sender
-(void) changedProperty
{
[[NSNotificationCenter defaultCenter] postNotificationName:#"NotificationName" object:NULL];
}
And here the code to receive this notification:
#interface Listener : UIViewController
{
}
#implementation Listener
- (void)viewDidLoad
{
[super viewDidLoad];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(selectedItem:) name:#"NotificationName" object:NULL];
}
- (void)viewDidUnload
{
[super viewDidUnload];
[[NSNotificationCenter defaultCenter] removeObserver:self name:#"NotificationName" object:NULL];
}
-(void) selectedItem:(NSNotification *) notification
{
// some actions
}
But this code doesn't work. Debugging I see how postNotificationName: object works but the method selectedItem: doesn't call
UPDATE.
Here is more code. Maybe this will help.
extern const NSString* selectItemNotificationName;
#interface vRoomSelectorItem : UIView
{
RoomSelectorItemBackground backgroundType;
NSInteger itemID;
}
#property NSInteger itemID;
-(void) setBackgroundType:(RoomSelectorItemBackground) backgroundType;
#interface vRoomSelectorItem ()
#property RoomSelectorItemBackground backgroundType;
#end
#implementation vRoomSelectorItem
const NSString* selectItemNotificationName = #"Reservation.SelectRoom";
-(RoomSelectorItemBackground) backgroundType
{
return backgroundType;
}
-(void) setBackgroundType:(RoomSelectorItemBackground)value
{
if(backgroundType != value)
{
backgroundType = value;
[self changedBackgroundType];
}
}
-(void) changedBackgroundType
{
if(backgroundType == RoomSelectorItemFilled)
{
// animation
dispatch_async(dispatch_get_main_queue(), ^{
[[NSNotificationCenter defaultCenter] postNotificationName:(NSString*)selectItemNotificationName object:NULL userInfo:[[NSDictionary alloc] initWithObjectsAndKeys:[NSNumber numberWithInteger:itemID], #"ID", NULL]];
});
}
else
// reverse animation
}
#import "vRoomSelectorItem.h"
#interface vcReservationSelectRoom : UIViewController
{
NSMutableArray* arraySelectorItems;
}
#implementation vcReservationSelectRoom
- (void)viewDidLoad
{
[super viewDidLoad];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(selectedItem:) name:(NSString*)selectItemNotificationName object:NULL];
for(NSInteger i = 1; i <= SELECTOR_ITEM_COUNT; ++i)
{
vRoomSelectorItem* newItem = [[vRoomSelectorItem alloc] initWithFrame:CGRectMake(/*coordinates*/)];
[self.view addSubview:newItem];
[newItem setBackgroundType:RoomSelectorItemTransparent];
[newItem setItemID:i];
[arraySelectorItems addObject:newItem];
newItem = NULL;
}
}
-(void) selectedItem:(NSNotification *) notification
{
// some actions
}
-(void) dealloc
{
arraySelectorItems = NULL;
[[NSNotificationCenter defaultCenter] removeObserver:self name:(NSString*)selectItemNotificationName object:NULL];
}
#end
From your code in the quetion I think you can try this:
- (void)viewDidLoad
{
[super viewDidLoad];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(selectedItem:) name:#"NotificationName" object:NULL];
[self.view changedProperty]; // method of your Sender class
}
It seems like your code should work. Make sure the notification is on the main thread and the workflow is as follows:
Add listener to notification center
Initiate sender
Send notification
You can be sure that it is on the main thread with:
dispatch_async(dispatch_get_main_queue(), ^{
[[NSNotificationCenter defaultCenter] post...];
});
Couple things I would change:
remove yourself from NSNotificationCenter in -(void)dealloc instead
of -(void)viewDidUnload. viewDidUnload will be deprecated, and
dealloc could get called without viewDidUnload.
For Notifications, I like to store the name in an external constant
to make sure that I don't typo the string:
//header.h
extern NSString *const notificationName;
//implementation.m
NSString *const notificationName = #"notification";
Ok, I've solved the problem. The piece of code above is not enough to understand, why it has not been working. The object of class vcReservationSelectRoom was temporary and it had been destroyed before sending notification from any vRoomSelectorItem. Sorry for my mistake of not showing enough code to solve this problem. And thank you all for helping.

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