swift判断app第一次启动

//appdelegate中写如下代码 func application(application: UIApplication,                     didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {    if  NSUserDefaults.standardUserDefaults().boolForKey("everLaunched") == false {        NSUserDefaults.standardUserDefaults().setBool(true, forKey: "everLaunched")        NSUserDefaults.standardUserDefaults().setBool(true, forKey: "firstLaunch")    }else{        NSUserDefaults.standardUserDefaults().setBool(false, forKey: "firstLaunch")    }    }

//在其他地方调用此方法进行判断func isFirstStartApp() -> Bool {      return NSUserDefaults.standardUserDefaults().boolForKey("firstLaunch")    }