How can I get the data?

You mean something like this?

    function visualTransform(options: VisualUpdateOptions, host: IVisualHost): BarChartViewModel {
        let dataViews = options.dataViews;
        let defaultSettings: BarChartSettings = {
            enableAxis: {
                show: false,
            }
        };
        let viewModel: BarChartViewModel = {
            dataPoints: [],
            dataMax: 0,
            settings: <BarChartSettings>{}
        }; 

        if (!dataViews
            || !dataViews[0]
            || !dataViews[0].categorical
            || !dataViews[0].categorical.categories
            || !dataViews[0].categorical.categories[0].source
            || !dataViews[0].categorical.values)
            return viewModel;

        let categorical = dataViews[0].categorical;
        let category = categorical.categories[0];
        let dataValue = categorical.values[0];

        let barChartDataPoints: BarChartDataPoint[] = [];
        let dataMax: number;

        let colorPalette: IColorPalette = host.colorPalette;
        let objects = dataViews[0].metadata.objects;
        let barChartSettings: BarChartSettings = {
            enableAxis: {
                show: getValue<boolean>(objects, 'enableAxis', 'show', defaultSettings.enableAxis.show),
            }
        }
        for (let i = 0, len = Math.max(category.values.length, dataValue.values.length); i < len; i++) {
            let defaultColor: Fill = {
                solid: {
                    color: colorPalette.getColor(category.values[i] + '').value
                }
            }

            barChartDataPoints.push({
                category: category.values[i] + '',
                value: dataValue.values[i],
                color: getCategoricalObjectValue<Fill>(category, i, 'colorSelector', 'fill', defaultColor).solid.color,
                selectionId: host.createSelectionIdBuilder()
                    .withCategory(category, i)
                    .createSelectionId()
            });
        }
        dataMax = <number>dataValue.maxLocal;

        return {
            dataPoints: barChartDataPoints,
            dataMax: dataMax,
            settings: barChartSettings,
        };
    }