app版本新特性

代码实例：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    
    NSString *key = @"CFBundleVersion";
    
    // 取出沙盒中存储的上次使用软件的版本号
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    NSString *lastVersion = [defaults stringForKey:key];
    
    // 获得当前软件的版本号
    NSString *currentVersion = [NSBundle mainBundle].infoDictionary[key];
    
    if ([currentVersion isEqualToString:lastVersion]) {
        // 显示状态栏
        application.statusBarHidden = NO;
        
        self.window.rootViewController = [[cctvTabBarViewController alloc] init];
    } else { // 新版本
        self.window.rootViewController = [[cctvNewfeatureViewController alloc] init];
        // 存储新版本
        [defaults setObject:currentVersion forKey:key];
        [defaults synchronize];
    }
    [self.window makeKeyAndVisible];
    return YES;
}