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Question

I need my app to constantly listen for reachability changes and update my views according to the network status , i am thinking about using the notificationcenter , and let all my views listen for changes, but i have no idea how to implement this.

I know how to use the notificationcenter and Reachability but i can't seem to find a place to implement the Reachability check .

Where should i check for network changes, and notify the other ViewControllers ?

I don't think AppDelegate is the right place, and if i put the Reachability check in a ViewController the network checking is only being performed as long as the ViewController is "active".

Answer 1

Create a "singleton" Reachability and initialize it at app launch.

Let the singleton check for reachability periodically, eg with NSTimer . It can then notify any other active views that registered with NSNotificationCenter .

// AppDelegate.m: 

@property (nonatomic, strong) Reachability *reachability;

// in applicationDidFinishLaunching...
self.reachability = [[Reachability alloc] init]; 

and

// Reachability.m

-(id)init {
   self = [super init];
   if (self) {
     [self setupTheTimer];
   }
   return self;
}

Answer 2

I would create a singleton NSObject class that handles all the network checks.

Name it like NetworkChecker.

Create a delegate for the callback, like NetworkCheckerDelegate with a method like:

@protocol NetworkCheckerDelegate <NSObject>

-(void)networkStatusUpdated:(NSInteger)networkStatus;

@end

@interface NetworkChecker : NSObject
{
    id<NetworkCheckerDelegate> networkDelegate;
}

Add a method to start the network checking and add a delegate to it like:

+(void)updateNetworkWithDelegate:(id<NetworkCheckerDelegate>)delegate
{
    networkDelegate = delegate;

    //Set timer to do Reachability checks
}

-(void)timerIsCompleted
{
    //Do Reachability check

    if( newNetworkState != oldNetworkState ){
        [networkDelegate networkStatusUpdated:newNetworkState];
    }
}

Then in each ViewController you need it you can do (do this in viewDidLoad):

[NetworkChecker updateNetworkWithDelegate:self];

And implement the following to do something after the network status changed:

-(void)networkStatusUpdated:(NSInteger)networkStatus