Run Internet Connection Check Throughout Entire App - iphone

Question

The method below works very well for checking to see if a user has an internet connection. I would like to check for an internet connection throughout my entire app, and am wondering if there is somewhere I can put it within my App Delegate where it will get called from every view controller.
Is there a way to do this? Doesn't seem to work properly if I put it in my applicationDidFinishLaunching. Any recommendations would be great! Thank you!
NSURL *scriptUrl = [NSURL URLWithString:#"http://www.google.com/m"];
NSData *data = [NSData dataWithContentsOfURL:scriptUrl];
if (data) {
NSLog(#"Device is connected to the internet");
}
else {
NSLog(#"Device is not connected to the internet");
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"No Internet Connectivity"
message:#"You must have an internet connection" delegate:self cancelButtonTitle:#"OK"
otherButtonTitles:nil, nil];
[alert show];
return;
}

Answer 1

If you're looking to place this particular method in a location that can be accessed and called from the entirety of your application then this is simply a design decision. There are a number of ways to achieve this.
I like to make use of the singleton paradigm when implementing global methods. John Wordsworth covers this in a nice succinct blog post here:
http://www.johnwordsworth.com/2010/04/iphone-code-snippet-the-singleton-pattern/
Here's a quick chunk of code:
InternetConnectionChecker.h
#import <Foundation/Foundation.h>
#interface InternetConnectionChecker : NSObject
// Accessor for singelton instance of internet connection checker.
+ (InternetConnectionChecker *)sharedInternetConnectionChecker;
// Check to see whether we have a connection to the internet. Returns YES or NO.
- (BOOL)connected;
#end
InternetConnectionChecker.m
#import "InternetConnectionChecker.h"
#implementation InternetConnectionChecker
// Accessor for singelton instance of internet connection checker.
+ (InternetConnectionChecker *)sharedInternetConnectionChecker
{
static InternetConnectionChecker *sharedInternetConnectionChecker;
#synchronized(self)
{
if (!sharedInternetConnectionChecker) {
sharedInternetConnectionChecker = [[InternetConnectionChecker alloc] init];
}
}
return sharedInternetConnectionChecker;
}
// Check to see whether we have a connection to the internet. Returns YES or NO.
- (BOOL)connected
{
NSURL *scriptUrl = [NSURL URLWithString:#"http://www.google.com/m"];
NSData *data = [NSData dataWithContentsOfURL:scriptUrl];
if (data) {
NSLog(#"Device is connected to the internet");
return TRUE;
}
else {
NSLog(#"Device is not connected to the internet");
return FALSE;
}
}
#end
In my example I've amended your method to return a true/false so you can handle the result within the UI calling the method appropriately but you could continue to show a UIAlertView if you pleased.
You would then use the singleton in the following way:
InternetConnectionChecker *checker = [InternetConnectionChecker sharedInternetConnectionChecker];
BOOL connected = [checker connected];

Answer 2

There are of course more complex ways of doing it, but the easiest way, (and the way I use) is to simply create a "CheckNetwork" class with your method as a class method which returns a bool, i.e:
+ (BOOL) checkConnection{
yourMethodDetails;
}
then simply #import "CheckNetwork.h" into any file in your project and call
if([CheckNetwork checkConnection]){
whatever you want to do here;
}

Answer 3

While Singleton class and Static methods are a way, you could also implement static inline methods in a .h file which as no .m file
Also, as a sidetalk, checking internet connectivity using using NSURL along with google.com is not a good practice.
Because,
It is not a simple ping operation
It downloads the whole page which may consume time
OS provided ways are more radical and appropriate.
It you are working with a specific web site, then using that web site for connectivity is the best practice, i think. See this Answer by Jon Skeet
I would suggest using the Reachability framework by Apple.
Or if you need more compact single function version, you could also use this function excerpted from Reachabilty myself
+ (BOOL) reachabilityForInternetConnection;
{
struct sockaddr_in zeroAddress;
bzero(&zeroAddress, sizeof(zeroAddress));
zeroAddress.sin_len = sizeof(zeroAddress);
zeroAddress.sin_family = AF_INET;
SCNetworkReachabilityRef reachability = SCNetworkReachabilityCreateWithAddress(kCFAllocatorDefault, (const struct sockaddr*)&zeroAddress);
SCNetworkReachabilityFlags flags;
if (SCNetworkReachabilityGetFlags(reachability, &flags))
{
return (flags & kSCNetworkReachabilityFlagsConnectionRequired);
}
return NO;
}