Healthkit: Data not showing first time running. - ios

Question

I have a strange problem when reading data out of healthkit. The first time when i press the button the weight is printed 0, the next times i press the button the weight is printed as normal.I would really appreciate it if someone could help me.
Thanks!
I have the following code.
HealtkitManager.h
#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
#import <HealthKit/HealthKit.h>
#interface HealthKitManager : NSObject
#property (nonatomic) float weight;
#property (nonatomic) HKHealthStore *healthStore;
+(HealthKitManager *)sharedManager;
-(void) requestAuthorization;
-(double) readWeight;
#end
Healthkitmanager.m
#import "HealthKitManager.h"
#import <healthKit/healthKit.h>
#import "StartScreen.h"
#interface HealthKitManager ()
#end
#implementation HealthKitManager
+(HealthKitManager *) sharedManager{
static dispatch_once_t pred = 0;
static HealthKitManager *instance = nil;
dispatch_once(&pred, ^{
instance = [[HealthKitManager alloc]init];
instance.healthStore = [[HKHealthStore alloc]init];
});
return instance;
}
-(void)requestAuthorization {
if([HKHealthStore isHealthDataAvailable]==NO){
return;
}
NSArray *readTypes = #[[HKObjectType quantityTypeForIdentifier:HKQuantityTypeIdentifierBodyMass],
[HKObjectType quantityTypeForIdentifier:HKQuantityTypeIdentifierBodyMassIndex],
[HKObjectType quantityTypeForIdentifier:HKQuantityTypeIdentifierBodyFatPercentage]];
[self.healthStore requestAuthorizationToShareTypes:nil readTypes:[NSSet setWithArray:readTypes] completion:nil];
}
-(double) readWeight{
NSMassFormatter *massFormatter = [[NSMassFormatter alloc]init];
massFormatter.unitStyle = NSFormattingUnitStyleLong;
HKQuantityType *weightType = [HKQuantityType quantityTypeForIdentifier:HKQuantityTypeIdentifierBodyMass];
[self fetchMostRecentDataOfQuantityType:weightType withCompletion:^(HKQuantity *mostRecentQuantity, NSError *error) {
if(!mostRecentQuantity){
NSLog(#"%#",#"Error. ");
}
else{
HKUnit *weightUnit = [HKUnit gramUnit];
_weight = [mostRecentQuantity doubleValueForUnit:weightUnit];
_weight = (float)_weight/1000.00f;
}
}];
return _weight;
}
- (void)fetchMostRecentDataOfQuantityType:(HKQuantityType *)quantityType withCompletion:(void (^)(HKQuantity *mostRecentQuantity, NSError *error))completion {
NSSortDescriptor *timeSortDescriptor = [[NSSortDescriptor alloc] initWithKey:HKSampleSortIdentifierEndDate ascending:NO];
HKSampleQuery *query = [[HKSampleQuery alloc] initWithSampleType:quantityType predicate:nil limit:1 sortDescriptors:#[timeSortDescriptor] resultsHandler:^(HKSampleQuery *query, NSArray *results, NSError *error) {
if (!results) {
if (completion) {
completion(nil, error);
}
return;
}
if (completion) {
HKQuantitySample *quantitySample = results.firstObject;
HKQuantity *quantity = quantitySample.quantity;
completion(quantity, error);
}
}];
[self.healthStore executeQuery:query];
}
#end
Startscreen.m
#import "StartScreen.h"
#import "HealthKitManager.h"
#interface StartScreen ()
#property(nonatomic,weak) IBOutlet UILabel *weightLabel;
#end
#implementation StartScreen
- (void)viewDidLoad {
[super viewDidLoad];
[[HealthKitManager sharedManager] requestAuthorization];
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
-(IBAction)readAgeButtonPressed:(id)sender{
HealthKitManager *readWeight = [[HealthKitManager sharedManager] init];
NSLog(#"%.2f",readWeight.readWeight);
}
#end

Answer 1

You use singleton HealthKitManager but your code
HealthKitManager *readWeight = [[HealthKitManager sharedManager] init];
in IBAction readAgeButtonPressed should be
HealthKitManager *readWeight = [HealthKitManager sharedManager];
You don't need init.
Also, you can change the code
[[HealthKitManager sharedManager] requestAuthorization];
to be
HealthKitManager *readWeight = [HealthKitManager sharedManager];
[readWeight requestAuthorization];
NSLog(#"%.2f",readWeight.readWeight);
checking the value of readWeight.