- (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;
}

swift版本看起来像这样：

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()
}