Custom visual tooltip service not working

Copied tooltipServiceWrapper.ts file from https://github.com/Microsoft/PowerBI-visuals-sampleBarChart and pasted in my src folder.
Added "src/tooltipServiceWrapper.ts" to tsconfig.json files part.

Below is my visual.ts. Please let me know if I'm missing anything.
Now, the visual doesn't show anything. If I comment the first line in the constructor the bar graph shows without tooltips.

module powerbi.extensibility.visual {
    "use strict";
	
	import ValueFormatter = powerbi.extensibility.utils.formatting.valueFormatter;
	
	export interface BarData {
		Indicator: number;
		Category: string;
	  }
	
  export class Visual implements IVisual {
	  private svg: d3.Selection<SVGElement>; 
	  private g: d3.Selection<SVGElement>;
	  private host: IVisualHost;
	  private tooltipServiceWrapper: ITooltipServiceWrapper;	
	  private bColorPos: string;
	  private bColorNeg: string; 
	  
	constructor(options: VisualConstructorOptions) {
		this.tooltipServiceWrapper = createTooltipServiceWrapper(this.host.tooltipService, options.element);
		this.svg = d3.select(options.element).append('svg');
		this.g = this.svg.append('g');
        this.bColorPos = "#32CD32";
		this.bColorNeg = "#FD625E";
	}
	  
	  
  	public update(options: VisualUpdateOptions) {
			this.setObjectProperties(options);
			this.generateBarChart(options);
		}
		

	public setObjectProperties(options: VisualUpdateOptions) {
			if (options.dataViews[0].metadata.objects)
				{
					if (options.dataViews[0].metadata.objects["bar"] && options.dataViews[0].metadata.objects["bar"]["bColorPos"]) {this.bColorPos = options.dataViews[0].metadata.objects["bar"]["bColorPos"]["solid"]["color"].toString();}
					if (options.dataViews[0].metadata.objects["bar"] && options.dataViews[0].metadata.objects["bar"]["bColorNeg"]) {this.bColorNeg = options.dataViews[0].metadata.objects["bar"]["bColorNeg"]["solid"]["color"].toString();}
				}
	  	}		
	  

	public generateBarChart(options: VisualUpdateOptions){

			
			
			var _this = this;
			var barColor1 = this.bColorPos;
			var barColor2 = this.bColorNeg;

			_this.svg.attr({
				height: options.viewport.height,
				width: options.viewport.width
			});

			var gHeight = options.viewport.height * 0.5;
			var gWidth = options.viewport.width ;

			_this.g.attr({
				height: gHeight,
				width: gWidth
			});

			_this.g.attr('transform','translate(0,0)');

			// convert data format
			var data = Visual.dataForBarGraph(options);

			// setup d3 scale
			var xScale = d3.scale.ordinal()
				.domain(data.map(function (d) { return d.Category; }))
				.rangeRoundBands([0, gWidth], 0.1);
			var yMax =
				d3.max(data, function (d) { return d.Indicator });
			var yScale = d3.scale.linear()
				.domain([0, yMax])
				.range([gHeight, 0])

				// remove exsisting axis and bar
			_this.svg.selectAll('.bar').remove();

			// draw bar
			var shapes = _this.g
				.append('g')
				.selectAll('.bar')
				.data(data);

			shapes.enter()
				.append('rect')
				.attr('class', function (d) { return d.Indicator < 0 ? "bar negative" : "bar positive"; })
				.attr('fill', function (d) { return d.Indicator < 0 ? barColor2 : barColor1; })
				.attr('x', function (d) { return xScale(d.Category); })
				.attr('width', xScale.rangeBand())
				.attr('y', function (d) { return d.Indicator < 0 ? yScale(0) : yScale(d.Indicator); })
				.attr('height', function (d) { return d.Indicator < 0 ?  yScale(d.Indicator) - yScale(0) : gHeight - yScale(d.Indicator); })
			
			this.tooltipServiceWrapper.addTooltip(this.svg.selectAll('.bar'), 
            (tooltipEvent: TooltipEventArgs<number>) => Visual.getTooltipData(tooltipEvent.data),
			(tooltipEvent: TooltipEventArgs<number>) => null);
				
			shapes.exit().remove();
		}


	public static dataForBarGraph(options: VisualUpdateOptions): BarData[] {
			var resultData: BarData[] = [];
			var rows = options.dataViews[0].table.rows;
		
			for (var i = 0;i < rows.length;i++) {
				var row = rows[i];
					resultData.push({
						Indicator: +row[0].toString(),
						Category: row[2].toString()
						});
				
			}
			return resultData;
		}
		  



	public enumerateObjectInstances(options: EnumerateVisualObjectInstancesOptions): VisualObjectInstanceEnumeration {
		let objectName = options.objectName;
		let objectEnumeration: VisualObjectInstance[] = [];

		switch (objectName) {
			case 'bar':
				objectEnumeration.push({
				  objectName: objectName,
				  properties: {
					bColorPos: this.bColorPos,
					bColorNeg: this.bColorNeg,
				  },
				  selector: null
				});
			break;
		};

		return objectEnumeration; 
	}


	private static getTooltipData(value: any): VisualTooltipDataItem[] {
		return [{
			displayName: value.category,
			value: value.value.toString(),
			color: value.color
		}];
	}


	public destroy(): void {
		//TODO: Perform any cleanup tasks here
	}
	  
}
}