     }
     
     public func requestHealthKitPermission(completion: @escaping Callback<Bool>) {
+        guard (shareIdentifiers + readIdentifiers).count > 0 else {
+            debugCrash(message: "You should set shareIdentifiers or readIdentifiers --- Must request authorization for at least one data type")
+            return
+        }
+        
         store.requestAuthorization(
             toShare: types(identifiers: shareIdentifiers),
             read: types(identifiers: readIdentifiers)

    //
    open static let shared = SwiftyHealthKit()
    private init() {}
    fileprivate let store = HKHealthStore()
    
    fileprivate var shareIdentifiers: [HKQuantityTypeIdentifier] = []
    fileprivate var readIdentifiers: [HKQuantityTypeIdentifier] = []

        }
    }
    
    private func statistics(at date: Date, id: HKQuantityTypeIdentifier, option: HKStatisticsOptions, completion: @escaping Callback<HKStatistics?>) {
        
        statisticsCollection(at: date, id: id, option: option) { result in
            switch result {
