我在swift中使用GCD 像这样：
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)) {
//all background task
dispatch_async(dispatch_get_main_queue()) {
self.second()
}
}
在此代码中，第二个函数在完成所有后台任务之前被调用，这就是为什么我无法获取我在第二个函数中使用的某些数据的原因。我想完成所有后台任务后的第二种方法。谁能告诉我如何完成这项任务呢？
***************在后台我正在使用像******这样的健康套件数据
let healthKitTypesToRead =
Set(
arrayLiteral: HKObjectType.characteristicTypeForIdentifier(HKCharacteristicTypeIdentifierDateOfBirth)!,
HKObjectType.characteristicTypeForIdentifier(HKCharacteristicTypeIdentifierBiologicalSex)!,
HKObjectType.workoutType()
)
let newCompletion: ((Bool, NSError?) -> Void) = {
(success, error) -> Void in
if !success {
print("You didn't allow HealthKit to access these write data types.\nThe error was:\n \(error!.description).")
return
}
else
{
let stepCount = HKSampleType.quantityTypeForIdentifier(HKQuantityTypeIdentifierStepCount)
// Our search predicate which will fetch data from now until a day ago
// (Note, 1.day comes from an extension
// You'll want to change that to your own NSDate
//let date = NSDate()
//let predicate = HKQuery.predicateForSamplesWithStartDate(date, endDate: NSDate(), options: .None)
// The actual HealthKit Query which will fetch all of the steps and sub them up for us.
let stepCountQuery = HKSampleQuery(sampleType: stepCount!, predicate:.None, 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())
}
testClass.HK_stepCount = String(steps)
}
//completion(steps, error)
}
self.healthKitStore.executeQuery(stepCountQuery)
//EDIT.....
let tHeartRate = HKSampleType.quantityTypeForIdentifier(HKQuantityTypeIdentifierHeartRate)
let tHeartRateQuery = HKSampleQuery(sampleType: tHeartRate!, predicate:.None, limit: 0, sortDescriptors: nil) { query, results, error in
if results?.count > 0
{
var string:String = ""
for result in results as! [HKQuantitySample]
{
let HeartRate = result.quantity
string = "\(HeartRate)"
print(string)
}
testClass.HK_HeartRate = string
finalCompletion(Success: true)
}
}
self.healthKitStore.executeQuery(tHeartRateQuery)
}
}
healthKitStore.requestAuthorizationToShareTypes(healthKitTypesToWrite, readTypes: healthKitTypesToRead, completion: newCompletion)
我无法获取步数值，它在调用第二个（方法）后执行，plz建议我该怎么做？
答案 0 :(得分：1)
您可以创建一个单独的函数来在其他线程上执行任务
func someFunction(finalCompletion: (Success: Bool)->()) {
let healthKitTypesToRead =
Set(
arrayLiteral: HKObjectType.characteristicTypeForIdentifier(HKCharacteristicTypeIdentifierDateOfBirth)!,
HKObjectType.characteristicTypeForIdentifier(HKCharacteristicTypeIdentifierBiologicalSex)!,
HKObjectType.workoutType()
)
let newCompletion: ((Bool, NSError?) -> Void) = {
(success, error) -> Void in
if !success {
print("You didn't allow HealthKit to access these write data types.\nThe error was:\n \(error!.description).")
return
}
else
{
let stepCount = HKSampleType.quantityTypeForIdentifier(HKQuantityTypeIdentifierStepCount)
// Our search predicate which will fetch data from now until a day ago
// (Note, 1.day comes from an extension
// You'll want to change that to your own NSDate
//let date = NSDate()
//let predicate = HKQuery.predicateForSamplesWithStartDate(date, endDate: NSDate(), options: .None)
// The actual HealthKit Query which will fetch all of the steps and sub them up for us.
let stepCountQuery = HKSampleQuery(sampleType: stepCount!, predicate:.None, limit: 0, sortDescriptors: nil) { query, results, error in
var steps: Double = 0
if results?.count > 0
{
// Edit--
for result in results as! [HKQuantitySample]
{
steps += result.quantity.doubleValueForUnit(HKUnit.countUnit())
// heartBeat += ....
}
testClass.HK_stepCount = String(steps)
finalCompletion(Success: true)
}
//completion(steps, error)
}
self.healthKitStore.executeQuery(stepCountQuery)
}
}
healthKitStore.requestAuthorizationToShareTypes(healthKitTypesToWrite, readTypes: healthKitTypesToRead, completion: newCompletion)
}
另一个功能？
我会在一段时间内编辑这个答案，告诉你一个更好的技术来处理异步请求。通常，您应该为此类后台任务设置单独的单例类。 （RESTful API服务类..但是现在你可以使用以下方法）
func getHeartBeatInfo(finalCompletionHeart: (Success: Bool)->()) {
let tHeartRate = HKSampleType.quantityTypeForIdentifier(HKQuantityTypeIdentifierHeartRate)
let tHeartRateQuery = HKSampleQuery(sampleType: tHeartRate!, predicate:.None, limit: 0, sortDescriptors: nil) { query, results, error in
if results?.count > 0
{
var string:String = ""
for result in results as! [HKQuantitySample]
{
let HeartRate = result.quantity
string = "\(HeartRate)"
print(string)
}
testClass.HK_HeartRate = string
finalCompletionHeart(Success: true)
}
}
self.healthKitStore.executeQuery(tHeartRateQuery)
}
然后你可以像这样调用这个方法：
override func viewDidLoad() {
someFunction( { (finalCompletion) in
if finalCompletion == true {
getHeartBeatInfo( { finalCompletionHeart in
if finalCompletionHeart == true {
self.second()
}
})
}
})
}