hk_shared_manager_1.h

#import <Foundation/Foundation.h>

@interface HealthKitManager : NSObject

// shared instance
+ (HealthKitManager *)sharedInstance;

@end

hk_shared_manager_1.m

#import "HealthKitManager.h"
#import <HealthKit/HealthKit.h>

@interface HealthKitManager ()
@property (nonatomic, retain) HKHealthStore *healthStore;
@end

@implementation HealthKitManager
// shared instance
+ (HealthKitManager *)sharedInstance {
    static HealthKitManager *instance = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        instance = [[HealthKitManager alloc] init];
    });
    return instance;
}

// init
- (id)init {
    self = [super init];
    if (self) {
        self.healthStore = [[HKHealthStore alloc] init];
    }
    return self;
}
@end