Quick and dirty import of CSV data into HealthKit .bodyMass measurements. I used this to import my Withings health data export.

HealthKitImport.swift

/**
 Quick and dirty CSV importer, only used once by me to import my own data, sharing it here
 in case anyone finds it useful.
*/
class HealthKitCSVImporter {

    let healthStore = HKHealthStore()
    let bodyMassType = HKSampleType.quantityType(forIdentifier: .bodyMass)!
    
    func authorizeHealthKit(completion: @escaping ((_ success: Bool, _ error: Error?) -> Void)) {
        
        if !HKHealthStore.isHealthDataAvailable() {
            return
        }
        
        let readDataTypes: Set<HKSampleType> = [bodyMassType]
        
        healthStore.requestAuthorization(toShare: nil, read: readDataTypes) { (success, error) in
            completion(success, error)
        }
    }
        
    
    func importData() {
        healthStore.requestAuthorization(toShare: [bodyMassType], read: [bodyMassType], completion: { (success, error) in
            if success {
                // Load "weight.csv" from the app bundle
                guard let path = Bundle.main.path(forResource: "weight", ofType: "csv") else {
                    return
                }
                
                // Convert CSV data into UTF-8 string, split it at newlines
                let csvData = try! Data.init(contentsOf: URL(fileURLWithPath: path))
                let csvString = String(data: csvData, encoding: .utf8)!
                let lines = csvString.split(separator: "\n")
                var lineNum = 0
                                
                // Walk each line after the first, turning each row into a .bodyMass sample
                var records = [HKObject]()
                lines.forEach { line in
                    lineNum = lineNum + 1
                    if (lineNum > 1) {
                        // Split into comma-separated fields
                        let fields = line.split(separator:",")
                      
                        // Fields are quoted, so remove the quotes
                        let dateStr = fields[0].replacingOccurrences(of: "\"", with: "")
                        let weightStr = fields[1].replacingOccurrences(of: "\"", with: "")
                        
                        // Dates in my file are formatted "2016-03-23 17:40:23", set up a DateFormatter to parse
                        let dateFormatter = DateFormatter()
                        dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
                        let date = dateFormatter.date(from:String(dateStr))!

                        // Weight is in pounds
                        let weight = Double(weightStr)!

                        NSLog("Date: \(date), weight: \(weight)")

                        let bodyMassSample = HKQuantitySample(type: self.bodyMassType,
                                                                   quantity: HKQuantity(unit: HKUnit.pound(), doubleValue: weight),
                                                                   start: date,
                                                                   end: date)
                        records.append(bodyMassSample)
                    }
                }

                // Save all the records to HealthKit
                self.healthStore.save(records, withCompletion: { (succ, err) in
                    NSLog("All done, error=\(err)")
                })
            }
        })
    }
}