【Objective-C】時間によって照度を変更する方法

    //時間の設定値（アプリの設定で入力できるようにした）
    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
    NSString *startTime = [[userDefaults stringForKey: @"startTime"] stringByReplacingOccurrencesOfString:@":" withString:@""];
    NSString *endTime = [[userDefaults stringForKey: @"endTime"] stringByReplacingOccurrencesOfString:@":" withString:@""];
    
    NSDate *date = [NSDate date]; // 現在の日時を得る
    NSCalendar *calendar = [NSCalendar currentCalendar]; // カレントカレンダー取得
    NSCalendarUnit unit = NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit; //時分秒を指定
    NSDateComponents *dc = [calendar components:unit fromDate:date];
    
    NSString *hh = [NSString stringWithFormat:@"%02ld",[dc hour]];
    NSString *mm = [NSString stringWithFormat:@"%02ld",[dc minute]];
    NSString *ss = [NSString stringWithFormat:@"%02ld",[dc second]];
    
    NSString *now = [[hh stringByAppendingString:mm] stringByAppendingString:ss];

    if (startTime.intValue < endTime.intValue) {
        // 日をまたがない場合
        if (startTime.intValue <= now.intValue && now.intValue <= endTime.intValue) {
            //処理
            [[UIScreen mainScreen] setBrightness:0.0f];
        }else{
            [[UIScreen mainScreen] setBrightness:1.0f];
        }
    }else{
        // 日をまたぐ場合
        if (startTime.intValue <= now.intValue || now.intValue <= endTime.intValue) {
            //処理
            [[UIScreen mainScreen] setBrightness:0.0f];
        }else{
            [[UIScreen mainScreen] setBrightness:1.0f];
        }
    }