javascript - How to call New variable Class Name in coffeescript without eval -

so, have standard class extended child classes. in cases, i'm passing child class use through jquery option instead of using default standard class.

example: jquery('img').myplugin();

calls

new mainclass(arg1, arg2)

while

jquery('img').myplugin({classtouse : 'myextendedclass'});

calls

new myextendedclass(arg1, arg2)

here's code works, ugly in many ways. how can properly? here @settings simple object, , @settings.classtouse string that's passed.

@newclass = eval("new #{@settings.classtouse}(this.$element, this.settings)")

the following not work , returns string error:

@framer = new @settings['classtouse'](this.$element, this.settings)

a clipped version of full source code below. errors in logic result of clipping code code in current state 100% functional.

you can see code compiled here.

class mainclass   constructor: (@framedobject, @options) ->   dosomething: ->     alert('something')  class myextendedclass extends mainclass   dosomething: ->     alert('somethingdifferent')  class anotherextendedclass extends mainclass   dosomething: ->     super     alert('woah!')  $ ->   $.plugin = (element, options) ->     @settings = {classtouse : 'myextendedclass'} #built merging defaults , options     @init = ->             @mainclass = eval("new #{@settings.classtouse}(this.$element, this.settings)")     @init()       $.fn.mediaframe = (options) ->     return this.each ->       plugin = new $.plugin this, options 

how like:

class border   constructor: (@options) -> class redborder extends border     constructor: (@options) -> class blueborder extends border     constructor: (@options) ->  borders =    default: border   red: redborder   blue: blueborder  $.plugin = (element, options) ->   @mainclass = new borders[@settings.class || 'default'](@settings)