存在步数时，CMPedometer queryPedometerData() 返回 0 步数

Question

CMPedometer queryPedometerData() 方法中似乎存在错误。该方法在某些结束时间返回 0 步，但时间戳高于或低于 1 秒的相同查询返回正确的步数

例如

self.getStepsBetweenDates(NSDate(timeIntervalSince1970: 1543392126) as Date, date2:  NSDate(timeIntervalSince1970: 1543393044) as Date) returns (Int) 1488

self.getStepsBetweenDates(NSDate(timeIntervalSince1970: 1543392126) as Date, date2:  NSDate(timeIntervalSince1970: 1543393045) as Date) returns (Int) 0

self.getStepsBetweenDates(NSDate(timeIntervalSince1970: 1543392126) as Date, date2:  NSDate(timeIntervalSince1970: 1543393046) as Date) returns (Int) 1488

getStepsBetweenDates 方法如下所示

func getStepsBetweenDates(_ date1: Date, date2: Date) -> Int{

    let group = DispatchGroup()
    group.enter()

    var steps = 0

    self.pedometer.queryPedometerData(from: date1, to: date2, withHandler: {
      pData, error in
      if let e = error{
          print("Error querying pedometer", e.localizedDescription)
      }else{
        if let data = pData{
          steps = Int(data.numberOfSteps)
        }
        group.leave()
      }
    })

    _ = group.wait(timeout: DispatchTime.distantFuture)
    return steps

  }

Answer 1

queryPedometerData是异步调用

通常您不想返回getStepsBetweenDates 调用中的步骤，因为它是异步的。

如果您将var steps = 0 更改为var steps = [some random int]，那么由于设置了竞争条件，您很可能会得到该数字而不是 0。

更理想的做法是将您的代码实现为闭包/回调或其他形式的异步处理。

例如：

self.pedometer.queryPedometerData(from: date1, to: date2) { (data, error) in
  // Do something here with data.numberOfSteps    
}

这是 Medium 上关于异步代码的文章：

https://medium.com/ios-os-x-development/managing-async-code-in-swift-d7be44cae89f