PieChart: Identify univocally a specific entry

[gmoraleda]

While using the Charts library I'm having problems identifying an entry. I have an array of categories and an array of amounts in order to build a pie chart. When I tap an entry, I want to show the amount and the name of the category:

var cats: [String]! = ["Transport","Shopping","Food","Accomodation","Fun","Other"]
var expensesArray = [0.0, 0.0, 0.0, 0.0, 0.0, 0.0]

I fetch the values from Core Data:

func requestExp() {
        noExpView.isHidden = true
        pieChartView.isHidden = false

        total = 0
        trans = 0.0
        shop = 0.0
        food = 0.0
        acc = 0.0
        fun = 0.0
        other = 0.0

        // Create Fetch Request
        let fetchRequest: NSFetchRequest<Expense> = Expense.fetchRequest()
        // Create Predicate
        let predicate = NSPredicate(format: "%K >= %@ AND %K <= %@", argumentArray:["date", fromDate, "date", toDate])
        fetchRequest.predicate = predicate
        // Execute Fetch Request
        do {
            let result = try context.fetch(fetchRequest)

            for managedObject in result {
                if let amount = managedObject.value(forKey: "amount"), let currency = managedObject.value(forKey: "currency")
                {
                    switch managedObject.value(forKey: "Category") as! String {
                        case "Transportation":
                            trans+=amount as! Double
                        case "Shopping":
                            shop+=amount as! Double
                        case "Food":
                            food+=amount as! Double
                        case "Accomodation":
                            acc+=amount as! Double
                        case "Fun":
                            fun+=amount as! Double
                        case "Other":
                            other+=amount as! Double
                    default:
                            break
                    }
                    print("\(amount) \(currency)")
                    total+=amount as! Double
                }
            }
            expensesArray = [trans, shop, food, acc, fun, other]
            print("Total for "+dateFormatter.string(from: fromDate)+" to "+dateFormatter.string(from: toDate)+" = "+String(total))

            let final = formatter.string(from: total as NSNumber)
            totalLabel.text = final
            let dayAverage = total / calcDays()
            average.text = formatter.string(from: dayAverage as NSNumber)
            average.isHidden = false

            if total==0 {
                pieChartView.isHidden = true
                noExpView.isHidden = false
            }

        } catch {
            let fetchError = error as NSError
            print(fetchError)
        }

    }

    func setChart(dataPoints: [Double]) {
        
        
        var dataEntries: [ChartDataEntry] = []
        
        for i in 0..<dataPoints.count {
            let dataEntry = PieChartDataEntry(value: Double(dataPoints[i]), label: cats[i])
            dataEntries.append(dataEntry)
        }

        let pieChartDataSet = PieChartDataSet(values: dataEntries, label: nil)
        pieChartDataSet.colors = colors
        pieChartDataSet.drawValuesEnabled = false
        let data = PieChartData(dataSet: pieChartDataSet)
        pieChartView.data = data
        pieChartView.noDataText = "No data available"
        pieChartView.notifyDataSetChanged()

    }

This is my method to update the label which shows the category name. It doesn't work when I have 2 entries with the same value (since I'm using indexof, it shows the first one it finds in the array...) and I don't know how to address the issue:

func chartValueSelected(_ chartView: ChartViewBase, entry: ChartDataEntry, highlight: Highlight) {
        let style = NSMutableParagraphStyle()
        style.alignment = NSTextAlignment.center
        let centerText = NSMutableAttributedString()
        let category = NSMutableAttributedString(string: cats[expensesArray.index(of: entry.y)!] , attributes: [NSParagraphStyleAttributeName: style, NSForegroundColorAttributeName:UIColor.black,NSFontAttributeName: UIFont(name: "GillSans",size:19)!])
        let amount = NSMutableAttributedString(string: "\n"+formatter.string(from: entry.y as NSNumber)!, attributes: [NSParagraphStyleAttributeName: style, NSForegroundColorAttributeName:UIColor.black,NSFontAttributeName: UIFont(name: "GillSans",size:20)!])
        centerText.append(category)
        centerText.append(amount)
        pieChartView.centerAttributedText = centerText
    }

Thumbs up for this great library and thanks in advance for your help!

[gmoraleda]

Found the solution accessing directly the ChartDataEntry objects:
entry as! PieChartDataEntry).label
so, the whole chartValueSelected looks like this:

func chartValueSelected(_ chartView: ChartViewBase, entry: ChartDataEntry, highlight: Highlight) {
        let style = NSMutableParagraphStyle()
        style.alignment = NSTextAlignment.center
        let centerText = NSMutableAttributedString()
        let category = NSMutableAttributedString(string: (entry as! PieChartDataEntry).label!
, attributes: [NSParagraphStyleAttributeName: style, NSForegroundColorAttributeName:UIColor.black,NSFontAttributeName: UIFont(name: "GillSans",size:19)!])
        let amount = NSMutableAttributedString(string: "\n"+formatter.string(from: entry.y as NSNumber)!, attributes: [NSParagraphStyleAttributeName: style, NSForegroundColorAttributeName:UIColor.black,NSFontAttributeName: UIFont(name: "GillSans",size:20)!])
        centerText.append(category)
        centerText.append(amount)
        pieChartView.centerAttributedText = centerText
    }