BarLineScatterCandleBubbleRenderer.XBounds conformance to RangeExpression and Sequence

Sequence conformance simplifies for-in loops
Looking forward to when data types conforming to Collection, RangeExpression conformance by XBounds allows for slicing of the collections further simplifying algorithms on data/datasets.

Author: jjatie

Source/Charts/Renderers/BarLineScatterCandleBubbleRenderer.swift

@@ -78,12 +78,46 @@ open class BarLineScatterCandleBubbleRenderer: DataRenderer
             let low = chart.lowestVisibleX
             let high = chart.highestVisibleX
 
-            let entryFrom = dataSet.entryForXValue(low, closestToY: Double.nan, rounding: ChartDataSetRounding.down)
-            let entryTo = dataSet.entryForXValue(high, closestToY: Double.nan, rounding: ChartDataSetRounding.up)
+            let entryFrom = dataSet.entryForXValue(low, closestToY: .nan, rounding: .down)
+            let entryTo = dataSet.entryForXValue(high, closestToY: .nan, rounding: .up)
 
             self.min = entryFrom == nil ? 0 : dataSet.entryIndex(entry: entryFrom!)
             self.max = entryTo == nil ? 0 : dataSet.entryIndex(entry: entryTo!)
             range = Int(Double(self.max - self.min) * phaseX)
         }
     }
 }
+
+extension BarLineScatterCandleBubbleRenderer.XBounds: RangeExpression {
+    public func relative<C>(to collection: C) -> Swift.Range<Int>
+        where C : Collection, Bound == C.Index
+    {
+        return Swift.Range<Int>(min...min + range)
+    }
+
+    public func contains(_ element: Int) -> Bool {
+        return (min...min + range).contains(element)
+    }
+}
+
+extension BarLineScatterCandleBubbleRenderer.XBounds: Sequence {
+    public struct Iterator: IteratorProtocol {
+        private let bounds: BarLineScatterCandleBubbleRenderer.XBounds
+        private var value: Int
+
+        fileprivate init(bounds: BarLineScatterCandleBubbleRenderer.XBounds) {
+            self.bounds = bounds
+            self.value = bounds.min
+        }
+
+        public mutating func next() -> Int? {
+            guard value < bounds.max else { return  nil }
+            value += 1
+            return value
+        }
+    }
+
+    public func makeIterator() -> Iterator {
+        return Iterator(bounds: self)
+    }
+}

Source/Charts/Renderers/BubbleChartRenderer.swift

@@ -105,7 +105,7 @@ open class BubbleChartRenderer: BarLineScatterCandleBubbleRenderer
         let maxBubbleHeight: CGFloat = abs(viewPortHandler.contentBottom - viewPortHandler.contentTop)
         let referenceSize: CGFloat = min(maxBubbleHeight, maxBubbleWidth)
 
-        for j in stride(from: _xBounds.min, through: _xBounds.range + _xBounds.min, by: 1)
+        for j in _xBounds
         {
             guard let entry = dataSet.entryForIndex(j) as? BubbleChartDataEntry else { continue }
 
@@ -185,7 +185,7 @@ open class BubbleChartRenderer: BarLineScatterCandleBubbleRenderer
 
             let iconsOffset = dataSet.iconsOffset
 
-            for j in _xBounds.min..._xBounds.range + _xBounds.min
+            for j in _xBounds
             {
                 guard let e = dataSet.entryForIndex(j) as? BubbleChartDataEntry else { break }
 

Source/Charts/Renderers/CandleStickChartRenderer.swift

@@ -77,7 +77,7 @@ open class CandleStickChartRenderer: LineScatterCandleRadarRenderer
 
         context.setLineWidth(dataSet.shadowWidth)
 
-        for j in stride(from: _xBounds.min, through: _xBounds.range + _xBounds.min, by: 1)
+        for j in _xBounds
         {
             // get the entry
             guard let e = dataSet.entryForIndex(j) as? CandleChartDataEntry else { continue }
@@ -313,7 +313,7 @@ open class CandleStickChartRenderer: LineScatterCandleRadarRenderer
                 let lineHeight = valueFont.lineHeight
                 let yOffset: CGFloat = lineHeight + 5.0
 
-                for j in stride(from: _xBounds.min, through: _xBounds.range + _xBounds.min, by: 1)
+                for j in _xBounds
                 {
                     guard let e = dataSet.entryForIndex(j) as? CandleChartDataEntry else { break }
 

Source/Charts/Renderers/LineChartRenderer.swift

@@ -214,7 +214,7 @@ open class LineChartRenderer: LineRadarRenderer
             // let the spline start
             cubicPath.move(to: CGPoint(x: CGFloat(cur.x), y: CGFloat(cur.y * phaseY)), transform: valueToPixelMatrix)
 
-            for j in stride(from: (_xBounds.min + 1), through: _xBounds.range + _xBounds.min, by: 1)
+            for j in _xBounds.dropFirst()
             {
                 prev = cur
                 cur = dataSet.entryForIndex(j)
@@ -325,7 +325,7 @@ open class LineChartRenderer: LineRadarRenderer
                 _lineSegments = [CGPoint](repeating: CGPoint(), count: pointsPerEntryPair)
             }
 
-            for j in stride(from: _xBounds.min, through: _xBounds.range + _xBounds.min, by: 1)
+            for j in _xBounds
             {
                 var e: ChartDataEntry! = dataSet.entryForIndex(j)
 
@@ -391,7 +391,7 @@ open class LineChartRenderer: LineRadarRenderer
                 context.beginPath()
                 var firstPoint = true
 
-                for x in stride(from: _xBounds.min, through: _xBounds.range + _xBounds.min, by: 1)
+                for x in _xBounds
                 {
                     e1 = dataSet.entryForIndex(x == 0 ? 0 : (x - 1))
                     e2 = dataSet.entryForIndex(x)
@@ -544,7 +544,7 @@ open class LineChartRenderer: LineRadarRenderer
 
                 _xBounds.set(chart: dataProvider, dataSet: dataSet, animator: animator)
 
-                for j in stride(from: _xBounds.min, through: min(_xBounds.min + _xBounds.range, _xBounds.max), by: 1)
+                for j in _xBounds
                 {
                     guard let e = dataSet.entryForIndex(j) else { break }
 
@@ -649,7 +649,7 @@ open class LineChartRenderer: LineRadarRenderer
                 (dataSet.circleHoleColor == nil ||
                     dataSet.circleHoleColor == NSUIColor.clear)
 
-            for j in stride(from: _xBounds.min, through: _xBounds.range + _xBounds.min, by: 1)
+            for j in _xBounds
             {
                 guard let e = dataSet.entryForIndex(j) else { break }
 

Source/Charts/Renderers/ScatterChartRenderer.swift

@@ -151,7 +151,7 @@ open class ScatterChartRenderer: LineScatterCandleRadarRenderer
 
                 _xBounds.set(chart: dataProvider, dataSet: dataSet, animator: animator)
 
-                for j in stride(from: _xBounds.min, through: _xBounds.range + _xBounds.min, by: 1)
+                for j in _xBounds
                 {
                     guard let e = dataSet.entryForIndex(j) else { break }