Creating custom iOS-Charts renderer

Question

I'm using iOS-Charts library, and I need to subclass HorizontalBarChartRenderer so that I can change implementation of drawDataSet(...). This should be possible as stated before, like in this answer.

So I created my custom renderer, but because of access control and because I'm using Cocoapods I had to override little more than just drawDataSet:

fileprivate class Buffer
fileprivate var _buffers = Buffer
fileprivate func prepareBuffer(dataSet: IBarChartDataSet, index: Int)
fileprivate var _barShadowRectBuffer: CGRect = CGRect() open override
open override func drawDataSet(context: CGContext, dataSet: IBarChartDataSet, index: Int)

I didn't change anything yet, above methods were just copied from HorizontalBarChartRenderer, and I set renderer like this:

self.horizontalBarView.renderer = HorizontalBarStackRenderer(dataProvider: self.horizontalBarView, animator: self.horizontalBarView.chartAnimator, viewPortHandler: self.horizontalBarView.viewPortHandler).

When I try to run it, I get fatal error: Index out of range at BarCharRenderer's drawValues():

let buffer = _buffers[dataSetIndex]

When I tried to set renderer to standard HorizontalBarChartRenderer the same way:

self.horizontalBarView.renderer = HorizontalBarChartRenderer(dataProvider: self.horizontalBarView, animator: self.horizontalBarView.chartAnimator, viewPortHandler: self.horizontalBarView.viewPortHandler)

everything works fine. Am I missing something?

user_1095916 · Answer

How I made it work for bar charts:

Your custom renderer:

class RoundedBarChartRenderer: BarChartRenderer {

    private class Buffer {
       var rects = [CGRect]()
    }

    private var _buffers = [Buffer]()

    private var _barShadowRectBuffer: CGRect = CGRect()

    override func initBuffers() { /* copy everything from original file */ }

    override func drawDataSet(context: CGContext, dataSet: IBarChartDataSet, index: Int)
        { /* Copy everything */ }

    private func prepareBuffer(dataSet: IBarChartDataSet, index: Int)  { /* copy everything */ }

    override func drawValues(context: CGContext) { /* Copy everything */ }
}

Some parts will still not work properly, like accessibility. Comment out those part. Also, don't use any super.METHOD_NAME()

Creating custom iOS-Charts renderer

2 Answers