ios - CoreData 重复结果，时间戳谓词

Question

我有一个包含步骤和时间戳的数据库。例如，每条记录可能有 50 个步骤和一个时间戳。我正在尝试使用 NSPredicate 过滤这些记录以按小时过滤以显示条形图，然后显示当天的“总计”。

NSSortDescriptor *descriptor = [NSSortDescriptor sortDescriptorWithKey:@"timestamp" ascending:YES];

NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"Activity"];
fetchRequest.predicate = [NSPredicate predicateWithFormat:@"(timestamp >= %@) AND (timestamp <= %@)", from, to];
fetchRequest.sortDescriptors = @[descriptor];

NSArray *activities = [_managedObjectContext executeFetchRequest:fetchRequest error:&error];

从 日期和到 日期提供如下:

2015-03-07 05:00:00 +0000 - 2015-03-07 05:59:59 +0000

产生记录的结果:

Timestamp: 2015-03-07 05:59:53 +0000, Steps: 0   2015-03-07 05:00:00 +0000 - 2015-03-07 05:59:59 +0000

问题是，随着添加的steps 条目越多，“总”计数似乎会随着条目的增长而增加，增加一倍、三倍等。看来谓词可能根据时间戳重复计算某些记录。

从手机获取步数

- (void)getSteps
{
    __block NSInteger _numberOfSteps = 0;
    __block NSInteger _numberOfRest = 0;
    __block NSInteger _numberOfLow = 0;
    __block NSInteger _numberOfHigh = 0;

    __weak __typeof(self)weakSelf = self;
    [_activityManager queryActivityStartingFromDate:startDate toDate:endDate toQueue:[NSOperationQueue mainQueue] withHandler:^(NSArray *activities, NSError *error)
     {
         for (NSInteger i = 0; i < activities.count; i++)
         {
             CMMotionActivity *activity = activities[i];

             NSTimeInterval duration = 0.0;
             if (i < activities.count-1)
             {
                 CMMotionActivity *nextActivity = (CMMotionActivity *)activities[i+1];
                 duration = [nextActivity.startDate timeIntervalSinceDate:activity.startDate];
             }
             else
                 duration = [endDate timeIntervalSinceDate:activity.startDate];


             if (activity.walking)
                 _numberOfLow += round(duration);
             else if (activity.running)
                 _numberOfHigh += round(duration);
             else
                 _numberOfRest += round(duration);
         }

         if (activities.count == 0)
             _numberOfRest = (NSInteger)[weakSelf reportingInterval];

         if ( [endDate timeIntervalSinceDate:startDate] > [self reportingInterval] )
             _numberOfRest = [endDate timeIntervalSinceDate:startDate];


         [_stepCounter queryStepCountStartingFrom:startDate to:endDate toQueue:[NSOperationQueue mainQueue] withHandler:^(NSInteger numberOfSteps, NSError *error)
          {
              _numberOfSteps = numberOfSteps;

              // Nothing special, no calculations here, just creates record
              [self addSteps:@{@"timestamp":[ActivityEngine dateSpan:CDPDateSpanLocalTime],
                               @"steps":[NSString stringWithFormat:@"%ld", (long)_numberOfSteps],
                               @"rest":[NSString stringWithFormat:@"%ld", (long)_numberOfRest],
                               @"low":[NSString stringWithFormat:@"%ld", (long)_numberOfLow],
                               @"high":[NSString stringWithFormat:@"%ld", (long)_numberOfHigh]
                               }];
          }];
     }];
}

如何确保没有记录被重复计算？

Answer 1

在您的代码中，您遍历所有事件并查询特定日期范围。如果你反复这样做，你的步数肯定会增加一倍和三倍，等等。

确保以增量方式更新数据。错误的原因是您调用 getSteps 函数的方式和频率。或许您应该跟踪已存储的日期范围并从下一个查询中排除这些范围。