Problem using Charts in swift with blinking graph and no chart data available - swift

Question

I'm trying to show a pie chart using cocoapod Charts but I'm basically finding two problems. First of all, when the pie chart is showed for the first time it blinks for a couple of seconds. The chart it's in a tab bar so when I return to it there is no blink.
And secondly it is always showing the text "no chart data available" although the data is show. Please the picture I've attached.
Any suggestion?
import UIKit
import Charts
class PieChartViewController: UIViewController, ChartViewDelegate{
#IBOutlet weak var contenedorView: UIView!
#IBOutlet weak var pieChartView: PieChartView!
var nombres: [String]!
var precios: [Double]!
override func viewDidLoad() {
super.viewDidLoad()
pieChartView.delegate = self
nombres = eventos.devolverNombre()
precios = eventos.devolverPrecios()
//Configuramos el gráfico circular
setChart(dataPoints: nombres, values: precios)
self.pieChartView.noDataText = "Geen"
}
override func viewWillAppear(_ animated: Bool) {
reloadInputViews()
self.pieChartView.noDataText = "Geen"
contenedorView.layer.borderWidth = 2
contenedorView.layer.borderColor = UIColor.white.cgColor
contenedorView.layer.cornerRadius = 10
self.view.aplicarFondoDegradado()
}
func setChart(dataPoints: [String], values: [Double]) {
var dataEntries: [PieChartDataEntry] = []
for i in 0..<dataPoints.count {
let dataEntry = PieChartDataEntry(value: Double(i), label: dataPoints[i], data: dataPoints[i] as AnyObject)
if dataEntry != nil {
dataEntries.append(dataEntry)}
}
let chartDataSet = PieChartDataSet(entries: dataEntries, label: "PRECIOS POR EVENTO")
let chartData = PieChartData(dataSet: chartDataSet)
pieChartView.holeColor = UIColor.black
pieChartView.data = chartData
var colors: [UIColor] = []
for i in 0..<dataPoints.count {
let red = Double(arc4random_uniform(256))
let green = Double(arc4random_uniform(256))
let blue = Double(arc4random_uniform(256))
let color = UIColor(red: CGFloat(red/255), green: CGFloat(green/255), blue: CGFloat(blue/255), alpha: 1)
colors.append(color)
}
pieChartView.noDataText = ""
pieChartView.holeRadiusPercent = 0.6
pieChartView.legend.textColor = UIColor.white
pieChartView.legend.font = UIFont.systemFont(ofSize: 12)
pieChartView.drawEntryLabelsEnabled = false
chartDataSet.colors = colors
}
}