Check if my IOS application is updated

I need to check when my app launches if it was being updated, because i need to make a view that only appears when the app is firstly installed to appear again after being updated.

You could save a value (e.g. the current app version number) to NSUserDefaults and check it every time the user starts the app.

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    // ...

    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];

    NSString *currentAppVersion = [[NSBundle mainBundle] objectForInfoDictionaryKey:@"CFBundleShortVersionString"];
    NSString *previousVersion = [defaults objectForKey:@"appVersion"];
    if (!previousVersion) {
        // first launch

        // ...

        [defaults setObject:currentAppVersion forKey:@"appVersion"];
        [defaults synchronize];
    } else if ([previousVersion isEqualToString:currentAppVersion]) {
        // same version
    } else {
        // other version

        // ...

        [defaults setObject:currentAppVersion forKey:@"appVersion"];
        [defaults synchronize];
    }



    return YES;
}

The swift-2 version looks like this:

let defaults = NSUserDefaults.standardUserDefaults()

let currentAppVersion = NSBundle.mainBundle().objectForInfoDictionaryKey("CFBundleShortVersionString") as! String
let previousVersion = defaults.stringForKey("appVersion")
if previousVersion == nil {
    // first launch
    defaults.setObject(currentAppVersion, forKey: "appVersion")
    defaults.synchronize()
} else if previousVersion == currentAppVersion {
    // same version
} else {
    // other version
    defaults.setObject(currentAppVersion, forKey: "appVersion")
    defaults.synchronize()
}

The swift-3 version looks like this:

let defaults = UserDefaults.standard

let currentAppVersion = Bundle.main.object(forInfoDictionaryKey: "CFBundleShortVersionString") as! String
let previousVersion = defaults.string(forKey: "appVersion")
if previousVersion == nil {
    // first launch
    defaults.set(currentAppVersion, forKey: "appVersion")
    defaults.synchronize()
} else if previousVersion == currentAppVersion {
    // same version
} else {
    // other version
    defaults.set(currentAppVersion, forKey: "appVersion")
    defaults.synchronize()
}