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Replies:  1

What design pattern shall I use


I'm studying pattern and i want implement a class that build Charts.

In my case, charts could be made by legend, a description and a graphical representation(bar chart, line chart, pie chart). But I could create a chart without a legend, or without a description. So i have some variations to create the chart.

What pattern is better in these case ? I try the builder pattern but i cant make a concret class for all the combination that i have.

Sorry for the bad english.

I need some help, please.



Filipe Tatarli, Nov 16, 2011
Reply 1
Some indirect inputs that may be useful

Basically a chart is composed of
 -  An X- axis
 -  A Y- axis
 -  Or No Axis (Pie chart and others)
 -   Has a Title
 -   Has Legends
 -   Different renderings (bar, column, pie, candle-stick etc).
 -   Has model or data to bind to
 -   et el

If you analyze this you may observe that the only changing part in this is the rendering, i.e. a line chart, a pie chart etc rest other things are composable or in other words you may thing it this way...

A chart  has
-   a data to bind to
-   Render as

And is decorated with a 
- Title
- Axis
- Legends 

So, you can create various decorators for these elements and compose your main chart with these decorators at runtime and as and when required.

Approach 1 - Decorator pattern

The higher level API could be something like this

// Create a chart with legends
Chart lineChart = new LineChart();
ln.DataSource =  "Your datasource here";
lineChart.Render();   // Renders the linechart without legend

LegendsChart  ln = new LegendsChart(lineChart);

ln.Render();   // Renders the line chart with legends as well

Refer Decorator patterns here
You can add more decorators as needed without modifying your existing code

Approach 2 - Fluent API
It will look something like this
Chart lineChart  = new Linechart().ShowLegend();
linChartDataSource = "Your datasource here";


A good example of fluent interface can be found here..

NOTE:  This is just couple of  approaches, you an find numerous other approaches as well
Rajesh Pillai, Nov 21, 2011
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