d3 reusable chart: coffeescript

chart.coffee

class BaseChart

    constructor: ->
        @_width = 720
        @_height = 80

    draw: (selection) =>
        me = @
        selection.each( (d, i) -> me._draw(this, d, i) )

    _draw: (elem, d, i) ->
        throw "Not Implemented"

    width: (value) ->
        if not arguments.length
            return @_width
        @_width = value
        @

    height: (value) ->
        if not arguments.length
            return @_height
        @_height = value
        @


class MyChart extends BaseChart

    _draw: (elem, d, i) ->
        # generate chart here; `d` is the data and `elem` is the element


chart = new MyChart()
chart.width(800).height(120)
d3.select('body').datum(data).call(chart.draw)

Forked the gist to fix the two issues that you had with your implementation. Although, I think it's simpler to use the method that you presented. Hope this helps. Have you been using your Coffee version in your projects?