Reachability - Best practice before showing webView - iphone

Question

I would like to check "reachability" before/when a webView is shown in my app.
So far I've included the reachbility.h/.m files as well as added the SystemConfiguration.framework to the project.
And that's about where the agreements I have found on the internet end, from all of the posts and blogs etc. etc. everyone has a different idea/opinion of what to do after that. Additionally, I have found a lot partial code snippets that aren't really a complete solution, on which reachibility methods to call etc. etc. how to use them etc.
I have also found that some warn that you should try to reconnect before checking reachability...but I haven't found a consensus or a full solution. My app seems to reconnect to wifi without any extra code... so I'm a litte confused here too...
Any help to clear the muddy waters would be appreciated. I'm just looking for a simple straightforward solution.
Answer Accepted: I would like to note to newbies who may read this q/a later... that you will want to do the following:
Add this into your .h file:
- (BOOL) connectedToNetwork: (NSString *) remoteServer;
- (void) appLoadError: (NSString *) altertTitle alertMessage: (NSString *) altertMsg;
And you will need to import these at the top of your .m file:
sys/socket.h
netinet/in.h
netinet6/in6.h
arpa/inet.h
ifaddrs.h
netdb.h
SystemConfiguration/SystemConfiguration.h
Correct me if it is wrong... It seems to work fine for me...

Answer 1

I have always used this method in my App Delegate when I need to require Internet access. I have tuned it for different access types over time and it has served me well. It is a variant of one of the many methods you can find after a quick Google search on this topic.
It is a tricky thing to come up with a hard and fast strategy around this. The platform itself offers different connectivity options that have pros and cons based on the needs of each specific application. The method I use below is just a general connectivity test meaning the device can reach the Internet via some connectivity mechanism.
- (BOOL) connectedToNetwork: (NSString *) remoteServer {
// 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){
NSLog(#"Error. Could not recover network reachability flags");
return NO;
}
BOOL isReachable = flags & kSCNetworkFlagsReachable;
BOOL needsConnection = flags & kSCNetworkFlagsConnectionRequired;
BOOL nonWiFi = flags & kSCNetworkReachabilityFlagsTransientConnection;
NSURL *testURL = [NSURL URLWithString: remoteServer];
NSURLRequest *testRequest = [NSURLRequest requestWithURL:testURL cachePolicy:NSURLRequestReloadIgnoringLocalCacheData timeoutInterval:20.0];
NSURLConnection *testConnection = [[NSURLConnection alloc] initWithRequest:testRequest delegate:self];
return ((isReachable && !needsConnection) || nonWiFi) ? (testConnection ? YES : NO) : NO;
}
I usually call this inside applicationDidFinishLaunching. If the check returns false, I usually generate an error message (see below). This is because Apple forbids exiting the application by any means other than the home button on the device.
...
else if(![self connectedToNetwork: [NSString stringWithFormat: #"http://%#:%#/", sharedSettings.server, sharedSettings.port]]){
[self appLoadError: #"No Internet Detected" alertMessage:#"This application requires an active Internet connection. No content is available."];
}
...
- (void) appLoadError: (NSString *) altertTitle alertMessage: (NSString *) altertMsg {
UIAlertView *loadErr = [[UIAlertView alloc] initWithTitle: altertTitle message: altertMsg delegate: self cancelButtonTitle: #"OK" otherButtonTitles: nil];
[loadErr show];
[loadErr release];
// Load static screen
UIImage *image = [UIImage imageNamed:#"Error_NoInternet.png"];
UIImageView *imageView = [[UIImageView alloc] initWithImage:image];
[controller setNavigationBarHidden: YES animated: NO];
[window addSubview: imageView];
[imageView release];
}

Answer 2

Just a quick note, I believe that method is leaking an NSURLConnection on every call (at the bottom, testConnection).
You might want to use
+ (NSURLConnection *)connectionWithRequest:
(NSURLRequest *)request delegate:(id)delegate
instead.