我有一个收集步骤数据的函数，但我需要一种方法让它在循环之前等待查询完成。我意识到关于这个问题还有其他问题，但我不知道如何解决它。函数如下:
func stepsAllTime(completion: (Double, NSError?) -> () ) {
var stopStart = true
while stopStart {
x += -1
// The type of data we are requesting
let sampleType = HKSampleType.quantityTypeForIdentifier(HKQuantityTypeIdentifierStepCount)
var daysAgo = x
var daysSince = x + 1
var daysSinceNow = -1 * daysAgo
checker = allTimeSteps.count
// Our search predicate which will fetch data from now until a day ago
let samplePredicate = HKQuery.predicateForSamplesWithStartDate(NSCalendar.currentCalendar().dateByAddingUnit(.CalendarUnitDay, value: daysAgo, toDate: NSDate(), options: nil), endDate: NSCalendar.currentCalendar().dateByAddingUnit(.CalendarUnitDay, value: daysSince, toDate: NSDate(), options: nil), options: .None)
// The actual HealthKit Query which will fetch all of the steps and sub them up for us.
let stepQuery = HKSampleQuery(sampleType: sampleType, predicate: samplePredicate, limit: 0, sortDescriptors: nil) { query, results, error in
var steps: Double = 0
if results?.count > 0 {
for result in results as! [HKQuantitySample] {
steps += result.quantity.doubleValueForUnit(HKUnit.countUnit())
}
}
completion(steps, error)
self.allTimeStepsSum += steps
self.allTimeSteps.append(steps)
println("New Sum:")
println(self.allTimeStepsSum)
println("Days Since Today:")
println(daysSinceNow)
if !(self.allTimeStepsTotal > self.allTimeStepsSum) {
stopStart = false
}
}
if allTimeStepsTotal > allTimeStepsSum {
self.healthKitStore.executeQuery(stepQuery)
}
}
}
如何做到这一点？ Swift 中是否有某种“On Complete”函数？
最佳答案
我假设我的评论是准确的。 您可能想看一下递归模式，如下所示:
import HealthKit
class Person {
var nbSteps: Double = 0
func fetchInfo() -> Void {
let sampleType = HKSampleType()
let samplePredicate: NSPredicate? = nil // Your predicate
let stepQuery = HKSampleQuery(
sampleType: sampleType,
predicate: samplePredicate,
limit: 0,
sortDescriptors: nil) { (sampleQuery, object, error) -> Void in
self.nbSteps += 1 // or the value you're looking to add
dispatch_async(dispatch_get_main_queue(), { () -> Void in // Dispatch in order to keep things clean
self.fetchInfo()
})
}
}
}
关于ios - 如何等待异步函数 Swift，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/31551112/