CoreData to CSV file code walkthrough

Code for CoreData Video Walkthrough

// MARK: Export functions
    
    func createExportString() -> String {
        var date: NSDate? = NSDate()
        var worktime: Double?
        var breaktime: Double?
        var studyRate: Double?
        var studyQuota: Double?
        var hoursLeft: Int?
        var distractionCount: Int?
        var breakCount: Int
        var longestStudy: Double
        var longestBreak: Double
        var totalStudyHours: Int
        var averageDailyStudyHours: Int
        
        var sessionArrayBool: [Bool]? = []
        var sessionArray: [Double]? = []
        
        var export: String = NSLocalizedString("date, hours studied, breaks, studyRate, study quota, hours left, number of distractions, breaks taken, longest study (hours), longest break (hours), hours studied (last 7 workdays), average study hours a day (last 7 workdays) \n", comment: "")
        for (index, day) in fetchedStatsArray.enumerate() {
            if index < fetchedStatsArray.count - 1 {
                date = day.valueForKey("date") as? NSDate
                worktime = day.valueForKey("workTotal") as? Double
                breaktime = day.valueForKey("breakTotal") as? Double
                studyRate = day.valueForKey("workRateActual") as? Double
                studyQuota = day.valueForKey("hourQuotaDay") as? Double
                if studyQuota != nil && worktime != nil {
                    hoursLeft = Int(studyQuota! - (worktime! / 3600) + 0.5)
                } else {
                    hoursLeft = nil
                }
                distractionCount = day.valueForKey("timeInBlock") as? Int
                sessionArray = day.valueForKey("sessionArray") as? [Double]
                sessionArrayBool = day.valueForKey("sessionArrayBool") as? [Bool]
                (longestStudy, longestBreak) = findMaxMinInArray(sessionArray, sessionArrayBool: sessionArrayBool)
                breakCount = countBreaksTaken(sessionArrayBool)
                averageDailyStudyHours = calculateAverageHoursLastSevenDays(fetchedStatsArray)
                totalStudyHours = calculateTotalHoursLastSevenDays(fetchedStatsArray)
                
                let dateString = "\(date!)" ?? "-"
                let worktimeString = "\(round(worktime! / 3600.00))" ?? "-"
                let breaktimeString = "\(round(breaktime! / 3600.00))" ?? "-"
                let studyRateString = "\(round(studyRate! * 100.00))" ?? "-"
                let studyQuotaString = "\(Int(studyQuota! + 0.5))" ?? "-"
                let hoursLeftString = "\(hoursLeft!)" ?? "-"
                let distractionCountString = "\(distractionCount!)" ?? "-"
                let longestStudyString = "\(round(longestStudy / 3600.00))" ?? "-"
                let longestBreakString = "\(round(longestBreak / 3600.00))" ?? "-"
                let breakCountString = "\(Int(breakCount))" ?? "-"
                let avStudyHoursString = "\(Int(averageDailyStudyHours))" ?? "-"
                let totalStudyHoursString = "\(totalStudyHours)" ?? "-"
                
                export += dateString + "," + worktimeString + "," + breaktimeString + "," + studyRateString + "%," + studyQuotaString + "," + hoursLeftString + "," + distractionCountString + "," + longestStudyString + "," + longestBreakString + "," + breakCountString + "," + avStudyHoursString + "," + totalStudyHoursString + "\n"
            }
        }
        print("This is what the app will export: \(export)")
        return export
    }
    
    func exportDatabase() {
        var exportString = createExportString()
        saveAndExport(exportString)
    }
    func saveAndExport(exportString: String) {
        let exportFilePath = NSTemporaryDirectory() + "export.csv"
        let exportFileURL = NSURL(fileURLWithPath: exportFilePath)
        NSFileManager.defaultManager().createFileAtPath(exportFilePath, contents: NSData(), attributes: nil)
        var fileHandleError: NSError? = nil
        var fileHandle: NSFileHandle? = nil
        do {
            fileHandle = try NSFileHandle(forWritingToURL: exportFileURL)
        } catch {
            print("Error with fileHandle")
        }
        
        if fileHandle != nil {
            fileHandle!.seekToEndOfFile()
            let csvData = exportString.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)
            fileHandle!.writeData(csvData!)
            
            fileHandle!.closeFile()
            
            let firstActivityItem = NSURL(fileURLWithPath: exportFilePath)
            let activityViewController : UIActivityViewController = UIActivityViewController(
                activityItems: [firstActivityItem], applicationActivities: nil)
            
            activityViewController.excludedActivityTypes = [
                UIActivityTypeAssignToContact,
                UIActivityTypeSaveToCameraRoll,
                UIActivityTypePostToFlickr,
                UIActivityTypePostToVimeo,
                UIActivityTypePostToTencentWeibo
            ]
            
            self.presentViewController(activityViewController, animated: true, completion: nil)
        }
    }