定時任務可以使用NSTimer.也可以使用本地推送UILocalNotification.

1.NSTimer
設定個時間就行了.(使用NSTimer的block初始化,要注意防止循環引用)

NSTimer *timer = [NSTimer timerWithTimeInterval:66 repeats:YES block:^(NSTimer * _Nonnull timer) {
    //執行你的代碼
 }];

當然也可以指定一個時間觸發.比如下方指定每天的某一點觸發(首先保證程序不被kill掉的情況下).

- (void)timingTask {
    //首先獲取一個時間
    NSDate *date = [NSDate date];
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateFormat:@"yyyy.MM.dd"];
    NSString *dateStr = [dateFormatter stringFromDate:date];
    //設置一個時間點. 比如 16:16:16
    NSString *newDateStr = [NSString stringWithFormat:@"%@ 16:16:16", dateStr];
    [dateFormatter setDateFormat:@"yyyy.MM.dd HH:mm:ss"];
    NSDate *newDate = [dateFormatter dateFromString:newDateStr];


    //然后初始化一個NSTimer.
    //一天的秒數是86400.然后設置重復repeats:YES.指定執行哪個方法.
    //最后添加到runloop就行了.從你運行代碼的當天起,就開始執行了.
    NSTimer *timer  = [[NSTimer alloc] initWithFireDate:newDate interval:10 target:self selector:@selector(timeTrigger) userInfo:nil repeats:YES];
    [[NSRunLoop currentRunLoop] addTimer:timer forMode:NSDefaultRunLoopMode];

}

- (void)timeTrigger {
    NSLog(@"觸發了");
}

2.UILocalNotification(類似鬧鐘的東西)
①.定時推送(http://www.lxweimin.com/p/3ed1db4fa538)

②.類似鬧鐘的(每天定時任務)

- (void)alarmClock {
    //首先獲取一個時間
    NSDate *date = [NSDate date];
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateFormat:@"yyyy.MM.dd"];
    NSString *dateStr = [dateFormatter stringFromDate:date];
    //設置一個時間點. 比如 16:16:16
    NSString *newDateStr = [NSString stringWithFormat:@"%@ 16:16:16", dateStr];
    [dateFormatter setDateFormat:@"yyyy.MM.dd HH:mm:ss"];
    NSDate *newDate = [dateFormatter dateFromString:newDateStr];
    
    //然后創建個本地推送.
    UILocalNotification *localNotification = [[UILocalNotification alloc] init];
    if (localNotification) {
        localNotification.fireDate = newDate;
        localNotification.timeZone = [NSTimeZone defaultTimeZone];
        localNotification.repeatInterval = NSCalendarUnitDay;//設置每天重復
        localNotification.alertTitle = @"鬧鐘";
        localNotification.alertBody = @"懶蟲起床了!~~";
        localNotification.alertAction = @"再睡會~";
        //如果有需要傳的東西可以設置一下userInfo
        localNotification.userInfo = @{@"key": @"value"};
        [[UIApplication sharedApplication] scheduleLocalNotification:localNotification];
    }
}

最后你每天就可以收到推送了.當然你也可以設置一下音頻,

 localNotification.soundName = UILocalNotificationDefaultSoundName;

但是如果需要將本地推送刪除或者替換掉.需要從本地通知數組中遍歷查找.然后再進行操作.

- (void)searchMyLocalNotification {
    NSArray *locArr = [[UIApplication sharedApplication] scheduledLocalNotifications];
    for (UILocalNotification *localNotification in locArr) {
        NSDictionary *userInfo = localNotification.userInfo;
        //你可以通過userInfo中的數據(key和value)來判斷是不是你想要的通知
        
        //然后你可以刪除此通知,或者將此通知替換掉
    }
}

刪除本地通知的代碼

[[UIApplication sharedApplication] cancelLocalNotification:localNotification];

注:以上有什么不對的地方,還請大家指出.共同進步啊!