Question

Ok so I am trying to get this app to show network error alert codes. I have added the SystemConfiguration.framework framework and Apple’s "Reachability" sample code.

Here is the viewcontroller.h file:

#import <UIKit/UIKit.h>

@class Reachability;

@interface Test_Internet_ConnectionViewController : UIViewController {

    Reachability* internetReachable;
    Reachability* hostReachable;
}

@property BOOL internetActive;
@property BOOL hostActive;

- (void) checkNetworkStatus:(NSNotification *)notice;

@end

Here is the viewcontroller.m file:

#import "Test_Internet_ConnectionViewController.h"
#import "Reachability.h";

@implementation Test_Internet_ConnectionViewController

@synthesize internetActive;
@synthesize hostActive;

/*
// The designated initializer. Override to perform setup that is required before the view is loaded.
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}
*/

/*
// Implement loadView to create a view hierarchy programmatically, without using a nib.
- (void)loadView {
}
*/


// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {
    [super viewDidLoad];

        // check for internet connection
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(checkNetworkStatus:) name:kReachabilityChangedNotification object:nil];

        internetReachable = [[Reachability reachabilityForInternetConnection] retain];
        [internetReachable startNotifier];

        // check if a pathway to a random host exists
        hostReachable = [[Reachability reachabilityWithHostName: @"www.apple.com"] retain];
        [hostReachable startNotifier];

        // now patiently wait for the notification
    }

/*
// Override to allow orientations other than the default portrait orientation.
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
    // Return YES for supported orientations
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}
*/

- (void)didReceiveMemoryWarning {
    // Releases the view if it doesn't have a superview.
    [super didReceiveMemoryWarning];

    // Release any cached data, images, etc that aren't in use.
}

- (void)viewDidUnload {
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}

- (void) checkNetworkStatus:(NSNotification *)notice
{
    // called after network status changes

    NetworkStatus internetStatus = [internetReachable currentReachabilityStatus];
    switch (internetStatus)

    {
        case NotReachable:
        {
            NSLog(@"The internet is down.");
            self.internetActive = NO;

            UIAlertView *errorView = [[UIAlertView alloc] initWithTitle:@"Internet Unavailable" message:@"This page cannot load, please check your internet connection and try again." delegate:nil cancelButtonTitle:@"Dismiss" otherButtonTitles:nil];
            [errorView show];
            [errorView release];

            break;

        }
        case ReachableViaWiFi:
        {
            NSLog(@"The internet is working via WIFI.");
            self.internetActive = YES;

            break;

        }
        case ReachableViaWWAN:
        {
            NSLog(@"The internet is working via WWAN.");
            self.internetActive = YES;

            break;

        }
    }

    NetworkStatus hostStatus = [hostReachable currentReachabilityStatus];
    switch (hostStatus)

    {
        case NotReachable:
        {
            NSLog(@"A gateway to the host server is down.");
            self.hostActive = NO;

            break;

        }
        case ReachableViaWiFi:
        {
            NSLog(@"A gateway to the host server is working via WIFI.");
            self.hostActive = YES;

            break;

        }
        case ReachableViaWWAN:
        {
            NSLog(@"A gateway to the host server is working via WWAN.");
            self.hostActive = YES;

            break;

        }
    }
}

- (void)dealloc {
    [super dealloc];

        [[NSNotificationCenter defaultCenter] removeObserver:self];

    }

@end

If there is no internet upon opening the app the error works as intended, but if the app loses connection after the it has initially opened with an internet connection the error displays 3 times, when I obviously only want it to display once.

I think it may be something in the Reachability class where it sends the notification 3 times, maybe in 3 different places. I don’t know why it does this, but I think the solution may be to remove the two calls I don’t want from the Reachability class but I don’t know how.

Can anyone help me, please?
Thanks in advance.

EDIT:

The 8 warnings and 4 errors are as follows:

‘TestViewController’ may not respond to ‘+checkConnectivity’

Initialization makes integer from pointer without a cast

Local declaration of ‘connectivity’ hides instance variable

‘MyReachability’ undeclared

‘reachability’ undeclared

‘TestViewController’ may not respond to ‘-siteAvailable’

‘TestViewController’ may not respond to ‘-addConnectivityView’

Redefinition of ‘-[TestViewController reachabilityChanged:]’

‘MyReachability’ undeclared

TestViewController may not respond to ‘-siteAvailable’

TestViewController may not respond to ‘-addConnectivityView’

TestViewController may not respond to ‘-removeConnectivityView’

Answer 1

Yes, it sends notifications multiple times for some reason. To overcome this I maintained a network status variable in application delegate, which was an observer for kReachabilityChangedNotification. The view was an observer for a custom kViewReachabilityChangedNotification, which was sent by an application delegate when the value actually changed. More than that, after getting a notification from reachability I called a Reachability function on getting a current network status and changed my application delegate variable accordingly. Then I could send a notification to a view to update itself.

This workaround is ugly, but works. I spent plenty of time on understanding why notifications being sent this way and finally gave up finding this solution.

EDIT:
Here’s your sample – I still don’t have a good place to put all working examples, so please try to figure out the solution from the code sample:
Subclass Reachability :

@interface MyReachability : Reachability
{
}
+(BOOL) connectedToNetwork;
@end

@implementation MyReachability

+ (BOOL) connectedToNetwork {
    // Create zero addy
    struct sockaddr_in zeroAddress;
    bzero(&zeroAddress, sizeof(zeroAddress));
    zeroAddress.sin_len = sizeof(zeroAddress);
    zeroAddress.sin_family = AF_INET;

    // Recover reachability flags
    SCNetworkReachabilityRef defaultRouteReachability = SCNetworkReachabilityCreateWithAddress(NULL, (struct sockaddr *)&zeroAddress);
    SCNetworkReachabilityFlags flags;

    BOOL didRetrieveFlags = SCNetworkReachabilityGetFlags(defaultRouteReachability, &flags);
    CFRelease(defaultRouteReachability);

    if (!didRetrieveFlags)
    {
        return NO;
    }

    BOOL isReachable = flags & kSCNetworkFlagsReachable;
    BOOL needsConnection = flags & kSCNetworkFlagsConnectionRequired;
    if (needsConnection && (flags & kSCNetworkReachabilityFlagsIsWWAN)) {
        needsConnection = NO;
    }
    return (isReachable && !needsConnection) ? YES : NO;
}

@end
In YourApplicationDelegate.h:

@interface YourApplicationDelegate :NSObject
{
     BOOL connectivity;
}
- (void) reachabilityChanged:(NSNotification *) note;
- (BOOL) checkConnectivity;
@end

In YourApplicationDelegate.m add function initReachability
call it to init your notifications from Reachability class.

- (void) initReachability
{
    MyReachability * reachability = [ MyReachability sharedReachability ];

    //[ reachability setHostName: [self hostName] ];
    [ reachability setNetworkStatusNotificationsEnabled: YES ];

    [self siteAvailable];

    NSNotificationCenter * notificationCenter = [ NSNotificationCenter defaultCenter ];
    [ notificationCenter addObserver: self
                            selector: @selector( reachabilityChanged: )
                                name: @"kNetworkReachabilityChangedNotification"
                              object: nil ];

    connectivity = [MyReachability testConnection:NO];
    if (!connectivity) {
        if (![MyReachability testConnection:NO]) {
            [self addConnectivityView];
        }
    }
}


- (BOOL) checkConnectivity
{
    return connectivity;
}

- (void) reachabilityChanged:(NSNotification *) note
{
    BOOL    newConnectivity = [MyReachability testConnection:NO];
    if (connectivity != newConnectivity) {
        connectivity = newConnectivity;
        [self siteAvailable];
        if (![MyReachability testConnection:NO]) {
            [self addConnectivityView];
        } else {
            [self removeConnectivityView];
            connectivity = YES;
            [[NSNotificationCenter defaultCenter] postNotificationName:@"kAppNetworkReachabilityChangedNotification" object:nil];
        }
    }
}

Pay attention, that @”kAppNetworkReachabilityChangedNotification” is a custom notification, that your view should subscribe to.

In your view controller’s viewDidLoad function:

-(void) viewDidLoad
{
       // your customization
    NSNotificationCenter * notificationCenter = [ NSNotificationCenter defaultCenter ];
    [ notificationCenter addObserver: self
                            selector: @selector( reachabilityChanged: )
                                name: @"kAppNetworkReachabilityChangedNotification"
                              object: nil ];

}


- (void) reachabilityChanged: (NSNotification *) note
{
    BOOL connectivity = [YourAppDelegate checkConnectivity];

    if (connectivity) {
           // update your view accordingly
    } 

}