Somebody give a Chart.controllers.bar.extend example?

I’m stuck in extend bar chart. I use codes below but not working…

    Chart.controllers.bar.extend({
        draw: function() {
            Chart.controllers.bar.prototype.draw.call(this, arguments);

            /* your own drawing code here */
            console.log(this); // but no any console log appear
        }
    });
    var sleepToday = new Chart(ctx, {
         type: 'bar',
         data: data,
         options: options
    });

Any ideas?

[snake]

Bump. Is there an issue with extension that is being looked at currently? Looking at the docs, it isn’t 100% clear as to the best approach to extending an existing chart type. Whilst the code posted by Rafael does achieve the extension (Thanks Rafael for posting that!), surely this isn’t the preferred means to extend? Like Iain said, it would be really nice to have a clear example in the docs.

For anyone who may stumble across this, here is how I created a new chart type based on the line chart. Credit to Rafael for pointing out that Chart.defaults needed to be set.

var baseController = Chart.controllers.line;
Chart.defaults.mytype = Chart.defaults.line;

Chart.controllers.mytype = Chart.controllers.line.extend({
    draw: function (ease) {
        baseController.prototype.draw.apply(this, arguments);

        // Draw other stuff here.
    }
});

[etimberg]

Rafael’s code is close to the recommended way to extend a chart type. I think there is a bug here because we shouldn’t cause a problem if the defaults are not defined. I’ve added comments for each line of the

// Sets the default config for 'myType' to be the same as the bubble defaults. 
// We look for the defaults by doing Chart.defaults[chartType]
// It looks like a bug exists when the defaults don't exist
Chart.defaults.myType = Chart.defaults.bubble;

// I think the recommend using Chart.controllers.bubble.extend({ extensions here });
var custom = Chart.DatasetController.extend(Chart.controllers.bubble.prototype);

// Overwrites the `linkScales` method. I don't think this is necessary and could cause problems
custom.linkScales = Chart.helpers.noop;

// Stores the controller so that the chart initialization routine can look it up with
// Chart.controllers[type]
Chart.controllers.myType = custom; 

I have an example of a chart derived from one of the existing types. I wrote a Smith Chart which derives from a line chart. I think you can use that as a partial reference for getting started.

If you don’t want to create a new chart, you would simply extend Chart.DatasetController to your liking. The API that needs to be implemented is documented at http://www.chartjs.org/docs/#advanced-usage-writing-new-chart-types