allow reference lines to be customized by NSNumberFormatterStyle

Classes/ScrollableGraphView.swift

@@ -148,6 +148,8 @@ import UIKit
     public var referenceLineUnits: String?
     /// The number of decimal places that should be shown on the reference line labels.
     public var referenceLineNumberOfDecimalPlaces: Int = 0
+    /// The NSNumberFormatterStyle that reference lines should use to display
+    public var referenceLineNumberStyle: NSNumberFormatterStyle = .NoStyle
 
     // Data Point Labels
     // #################
@@ -434,6 +436,7 @@ import UIKit
         referenceLineView?.labelFont = self.referenceLineLabelFont
         referenceLineView?.labelColor = self.referenceLineLabelColor
         referenceLineView?.labelDecimalPlaces = self.referenceLineNumberOfDecimalPlaces
+        referenceLineView?.labelNumberStyle = self.referenceLineNumberStyle
 
         referenceLineView?.setRange(self.range)
         self.addSubview(referenceLineView!)
@@ -1548,6 +1551,7 @@ private class ReferenceLineDrawingView : UIView {
     var labelFont: UIFont = UIFont.systemFontOfSize(8)
     var labelColor: UIColor = UIColor.blackColor()
     var labelDecimalPlaces: Int = 2
+    var labelNumberStyle: NSNumberFormatterStyle = .NoStyle
 
     // PRIVATE PROPERTIES
 
@@ -1631,8 +1635,10 @@ private class ReferenceLineDrawingView : UIView {
         let minLineStart = CGPoint(x: 0, y: self.bounds.height - bottomMargin)
         let minLineEnd = CGPoint(x: lineWidth, y: self.bounds.height - bottomMargin)
 
-        let maxString = String(format: "%.\(labelDecimalPlaces)f", arguments: [self.currentRange.max]) + units
-        let minString = String(format: "%.\(labelDecimalPlaces)f", arguments: [self.currentRange.min]) + units
+        let numberFormatter = referenceNumberFormatter()
+
+        let maxString = numberFormatter.stringFromNumber(self.currentRange.max)! + units
+        let minString = numberFormatter.stringFromNumber(self.currentRange.min)! + units
 
         addLineWithTag(maxString, from: maxLineStart, to: maxLineEnd, inPath: referenceLinePath)
         addLineWithTag(minString, from: minLineStart, to: minLineEnd, inPath: referenceLinePath)
@@ -1644,6 +1650,15 @@ private class ReferenceLineDrawingView : UIView {
         return referenceLinePath
     }
 
+    private func referenceNumberFormatter() -> NSNumberFormatter {
+        let numberFormatter = NSNumberFormatter()
+        numberFormatter.numberStyle = labelNumberStyle
+        numberFormatter.minimumFractionDigits = labelDecimalPlaces
+        numberFormatter.maximumFractionDigits = labelDecimalPlaces
+
+        return numberFormatter
+    }
+
     private func createIntermediateReferenceLines(rect: CGRect, numberOfIntermediateReferenceLines: Int, forPath path: UIBezierPath) {
 
         let height = rect.size.height
@@ -1692,7 +1707,8 @@ private class ReferenceLineDrawingView : UIView {
         if(shouldAddLabelsToIntermediateReferenceLines) {
 
             let value = calculateYAxisValueForPoint(lineStart)
-            var valueString = String(format: "%.\(labelDecimalPlaces)f", arguments: [value])
+            let numberFormatter = referenceNumberFormatter()
+            var valueString = numberFormatter.stringFromNumber(value)!
 
             if(shouldAddUnitsToIntermediateReferenceLineLabels) {
                 valueString += " \(units)"

README.md

@@ -173,6 +173,7 @@ The graph can be customised by setting any of the following public properties be
 | **shouldShowReferenceLineUnits**: Bool      | Whether or not to show the units on the reference lines.                                |
 | **referenceLineUnits**: String?             | The units that the y-axis is in. This string is used for labels on the reference lines. |
 | **referenceLineNumberOfDecimalPlaces**: Int | The number of decimal places that should be shown on the reference line labels.         |
+| **referenceLineNumberStyle**: NSNumberFormatterStyle | The number style that should be shown on the reference line labels.         |
 
 ### Data Point Labels (x-axis)