defaults.swift

func readSample(sampleType: HKSampleType, predicate: NSPredicate?, limit: Int?, completion: ((results: [HKSample]?, error: ErrorType?) -> Void)!) {
    // Read stored anchor (If this is the first run 0 will be returned which is equal to HKAnchoredObjectQueryNoAnchor)
    let anchorValue = defaults.integerForKey(sampleType.identifier)
    let limit = limit ?? Int(HKObjectQueryNoLimit)
    
    let query = HKAnchoredObjectQuery(type: sampleType, predicate: predicate, anchor: anchorValue, limit: limit) { (query, results, newAnchor, error) -> Void in
        guard let results = results where error == nil else {
            completion(results: nil, error: error)
            return
        }
        
        // Here I'm 'dynamically' creating new keys
        self.defaults.setInteger(newAnchor, forKey: sampleType.identifier)
        
        completion(results: results, error: nil)
    }
    
    healthKitStore.executeQuery(query)
}