How to datePicker indexing realm and drawing chart in swift3

Swift 3 , Realm, Charts

A screen has a DatePicker and BarChart

I want to

1) Pick a date 2) Indexing my realm database 3) Drawing a bar-chart

there already had a realm database

for indexing precise I separate date to YYYY~mm

class ChartsDatas: Object {
dynamic var date: Date = Date()

let dateYYYYFormat = DateFormatter()
let dateMMFormat = DateFormatter()
let dateddFormat = DateFormatter()
let datehhFormat = DateFormatter()
let datemmFormat = DateFormatter()
dynamic var dateYYYY: String = "2000"
dynamic var dateMM: String = "01"
dynamic var datedd: String = "01"
dynamic var datehh: String = "00"
dynamic var datemm: String = "00"

dynamic var count: Double = Double(0.0)

func dateLongToShort(orgDate:Date!){
    dateYYYYFormat.dateFormat = "YYYY"
    dateYYYY = dateYYYYFormat.string(from: orgDate)

    dateMMFormat.dateFormat = "MM"
    dateMM = dateMMFormat.string(from: orgDate)

    dateddFormat.dateFormat = "dd"
    datedd = dateddFormat.string(from: orgDate)

    datehhFormat.dateFormat = "hh"
    datehh = datehhFormat.string(from: orgDate)

    datemmFormat.dateFormat = "mm"
    datemm = datemmFormat.string(from: orgDate)
}

and drawing (This method is drawing newest ten datas)

    var dataEntries: [BarChartDataEntry] = []
    let visitorCounts = getVisitorCountsFromDatabase() //read realm DB here

    var xAxisCount = visitorCounts.count 
    if xAxisCount > 10{
        xAxisCount = visitorCounts.count - 10
    }
    for i in xAxisCount..<visitorCounts.count {
        let timeIntervalForDate: TimeInterval = visitorCounts[i].date.timeIntervalSince1970
        let dataEntry = BarChartDataEntry(x: Double(timeIntervalForDate), y: Double(visitorCounts[i].count))
        dataEntries.append(dataEntry)
    }

How to modify to drawing ten datas according to my chosen date

Thanks

Solution

I'm not sure what's going on in getVisitorCountsFromDatabase() but you can filter query results with predicate by specifying a date interval, see more in docs here: https://realm.io/docs/swift/latest/#filtering