NSString *latestVersionString - ios

Question

I am currently using this in my Xcode 5 application and I can't seem to get it working
NSString *bundleVersion = [[[NSBundle mainBundle] infoDictionary] objectForKey:#"CFBundleShortVersionString"];
NSString *latestVersionString = [NSString stringWithContentsOfURL:[NSURL URLWithString:#"http://mywebsite.com/version.txt"] encoding:NSUTF8StringEncoding error:nil];
#import NSString+compareToVersion.h
if ([bundleVersion isOlderThanVersion:latestVersionString]) {
// show a blocking modal view, with a button to link to the app store}

Answer 1

First, I do not recommend using synchronous network calls, regardless of how small the .txt file may be. You can try this for your code: Make sure to include <UIAlertViewDelegate> in your .h file first.
- (void)applicationDidBecomeActive:(UIApplication *)application
{
[[UIApplication sharedApplication]beginIgnoringInteractionEvents];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:
[NSURL URLWithString:#"http://mywebsite.com/version.txt"]];
request.timeoutInterval = 10.0;
request.cachePolicy = NSURLRequestReloadIgnoringLocalAndRemoteCacheData;
[NSURLConnection sendAsynchronousRequest:request
queue:[NSOperationQueue mainQueue]
completionHandler:
^(NSURLResponse *response, NSData *data, NSError *connectionError)
{
if (data)
{
NSString *bundleVersion = [[[NSBundle mainBundle] infoDictionary] objectForKey:#"CFBundleShortVersionString"];
NSString *latestVersionString = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];
if (![bundleVersion isEqualToString:latestVersionString])
{
// The two strings are not equal, dispatch to the UI thread and show a UIAlertView
dispatch_async(dispatch_get_main_queue(), ^
{
UIAlertView *alertView = [[UIAlertView alloc]initWithTitle:#"Update App!"
message:#"Please download the newer version available first on the App Store!"
delegate:self cancelButtonTitle:#"App Store"
otherButtonTitles:nil];
[alertView show];
[[UIApplication sharedApplication]endIgnoringInteractionEvents];
});
}
else
{
// Up to date; no new version is available, proceed to game play routines
[[UIApplication sharedApplication]endIgnoringInteractionEvents];
}
}
else
{
// No internet, or there is no data at the url, show error
// Uncomment below line if you want the user to interact with app again
// [[UIApplication sharedApplication]endIgnoringInteractionEvents];
}
}];
}
- (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex
{
[[UIApplication sharedApplication]openURL:[NSURL URLWithString:#"Your App Store app link here"]];
}

Answer 2

First, check the value of latestVersionString in the debugger. Make sure it is the value you want it to be (and not e.g. nil). Also, declare an NSError * to capture any error that arises from trying to initialise a string from an HTTP URL (consider the case where there may be no internet connection, or temporary routing or DNS issue etc.).
NSError *error = nil;
NSString *latestVersionString = [NSString stringWithContentsOfURL:[NSURL URLWithString:#"http://mywebsite.com/version.txt"] encoding:NSUTF8StringEncoding error:&error];
if (error != nil)
{
// figure out what went wrong based on the error
}
else
{
// check latestVersionString contains something valid and then compare
// with bundleVersion.
}
If both bundleVersion and latestVersionString contain what you expect, then the issue may be in the isOlderThanVersion: method.