Factory Method implementation in actionscript

Hey folks, i ve got this issue implementing the Factory method. Following is the snippet of the the main chart class which calls ChartFactory's method to attain the proper object. I Type Cast chartobject so as to be able to call the Show method;i m apprehensive about that as well.

        container = new VBox();
        container.percentWidth = 100;
        container.percentHeight = 100;
        super.media.addChild(container);

        chartObject = new ChartBase();
        chartObject = ChartFactory.CreateChartObject(chartType);
        IChart(chartObject).Show(o);
        container.addChild(chartObject);

        legend = new Legend();
        legend.dataProvider = IChart(chartObject);
        container.addChild(legend);

Following is the snippet of ChartFactory's method:

public static function CreateChartObject(subType:String):ChartBase
    {
         switch(subType)
         {
             case ChartFactory.AREA_CHART:
                 return new AreaCharts();
                 break;

             case ChartFactory.COLUMN_CHART:
                 return new ColumnCharts();
                 break;

             case ChartFactory.PIE_CHART:
                 return new PieCharts();
                 break;

             default:
                 throw new ArgumentError(subType + ": Chart type is not recognized.");
         }
    }

And following is Show method of one of the several Charts type classes: AreaCharts, PieCharts etc. All of which implements IChart Interface.

public function Show(o:ObjectProxy):void
    {
        var grids:GridLines;
        var stroke:SolidColorStroke;
        var horizontalAxis:CategoryAxis;
        var verticalAxis:LinearAxis;
        var horizontalAxisRenderer:AxisRenderer;
        var verticalAxisRenderer:AxisRenderer;

        grids = new GridLines();

        if(WidgetStylesheet.instance.LineChart_ShowGrid)
            grids.setStyle("gridDirection", "both");
        else
            grids.setStyle("gridDirection", "");

        stroke = new SolidColorStroke(WidgetStylesheet.instance.LineChart_GridLineColor, WidgetStylesheet.instance.LineChart_GridLineThickness);
        grids.setStyle("horizontalStroke", stroke);
        grids.setStyle("verticalStroke", stroke);

        horizontalAxis = new CategoryAxis();
        horizontalAxis.categoryField = o.LargeUrl.Chart.xField;
        horizontalAxis.title = o.LargeUrl.Chart.xAxisTitle.toString();
        verticalAxis = new LinearAxis();
        verticalAxis.title = o.LargeUrl.Chart.yAxisTitle.toString();

        horizontalAxisRenderer = new AxisRenderer();
        horizontalAxisRenderer.axis = horizontalAxis;
        horizontalAxisRenderer.setStyle("tickLength", 0);
        horizontalAxisRenderer.setStyle("showLine", false);
        hori开发者_开发百科zontalAxisRenderer.setStyle("showLabels", true);
        horizontalAxisRenderer.setStyle("fontSize", WidgetStylesheet.instance.ComputeChartAxisFontSize(o.HeadlineFontSize));
        verticalAxisRenderer = new AxisRenderer();
        verticalAxisRenderer.axis = verticalAxis;
        verticalAxisRenderer.setStyle("tickLength", 0);
        verticalAxisRenderer.setStyle("showLine", false);
        verticalAxisRenderer.setStyle("fontSize", WidgetStylesheet.instance.ComputeChartAxisFontSize(o.HeadlineFontSize));

        this.series = this.m_createSeries(o);
        this.horizontalAxis = horizontalAxis;
        this.horizontalAxisRenderers = [horizontalAxisRenderer];
        this.verticalAxis = verticalAxis;
        this.verticalAxisRenderers = [verticalAxisRenderer];
        this.backgroundElements = [grids];
    }

I'm afraid that there is more than one issue with this code. Unfortunately it is not obvious why your chart doesn't show up so you may apply some of advices below and use debugger to analyse the issue.

1. There is no point in creating ChartBase instance if you are going to change value of chartObject reference in the next line

   chartObject = new ChartBase();
   chartObject = ChartFactory.CreateChartObject(chartType);
   

2. If the API of your charts is IChart your factory should return IChart instead of casting.

   public static function CreateChartObject(subType:String):IChart
   

3. Make sure that you are returning instances of the correct class from the factory. i.e. that you are returning your subclass of standard PieChart. Generally it's not the best idea to extend the class keeping the same name and just changing the package.

4. Once again, if you are not sure if the program enters some function use the Flash Builder debugger to check this. I can't imagine development without debugger.

Some thoughts:

• you call the Show method, pass it some object but nowhere in that method is any child added to a displayObject. What exactly is Show supposed to do?

• a lot of member variables in your classes start with UpperCase. The compiler can easily confuse those with class names, in case your classes are named the same. Bad practice to start variable and function names with capitals.

• If your casting an instance to another class or interface fails, you will get a runtime error. Those are easy to debug using the Flash Builder debugger.

Hey ppl.. i found out wat wnt wrng..as olwys it wa "I". I ve a habit of mkin mock ups secluded from the main project n dn integrate it. So in mock up i hd used an xml whch hd a format slightly diff dn d one being used in the main project. N i hd a conditional chk to return from the prog if certain value doesnt match, n due to faulty xml i did'nt. So this more a lexical error than a logical one. Sorry n Thanx evryone for responding.