Execute a function after completing all background process in swift - ios

Question

I am using GCD in swift
like this :
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)) {
//all background task
dispatch_async(dispatch_get_main_queue()) {
self.second()
}
}
In this code second function is getting called before completing all background task that's why I am not able to take some data which I am using in second function. I want to second method after completing all background task. Can anyone tell me how to achieve this task?
***************In background I am taking healthkit data like******
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)
I am not able to take value of step count, It get executed after calling second(method) called, plz suggest me what to do?

Answer 1

You can create a separate function to execute your task on other thread
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)
}
Another function?
I will edit this answer in some time to tell you about a better technique to deal with async request. In general you should have a separate singleton class for such background tasks. (RESTful API service class.. but for now you can use the below method)
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)
}
And then you can call this method like so:
override func viewDidLoad() {
someFunction( { (finalCompletion) in
if finalCompletion == true {
getHeartBeatInfo( { finalCompletionHeart in
if finalCompletionHeart == true {
self.second()
}
})
}
})
}