getFillLinePosition not calling to create Area graph

[anishparajuli555]

i am trying to create an area graph. I subclassed ChartFillFormatter...But getFillLinePosition method is not calling??

public class BottomLineFillFormatter: NSObject, ChartFillFormatter
{
    private let chartView: LineChartView!
    init(chartViewInit: LineChartView) {
        chartView = chartViewInit
        super.init()
    }

    public func getFillLinePosition(dataSet dataSet: ILineChartDataSet, dataProvider: LineChartDataProvider) -> CGFloat{
        return CGFloat(chartView.leftAxis._axisMaximum)   
    }
}

My code to fill the line graph is as:

 let set3: LineChartDataSet = LineChartDataSet(yVals: yVals3, label:nil)
        set3.axisDependency = .Left // Line will correlate with left axis values
        set3.setColor(UIColor.grayColor().colorWithAlphaComponent(1.0))
        set3.lineWidth = 2.0
        set3.fillColor = UIColor.grayColor()
        set3.drawCirclesEnabled = false
        set3.fillFormatter = BottomLineFillFormatter(chartViewInit: lineChart)

[anishparajuli555]

I just need to set

set2.drawFilledEnabled = true