I'm trying to create a new type of filter using GridFilters to get a filter in multivalued fields. What i have done until now is to copy the ListFilter.js to a MultiListFilter.js, and modifying the next portions of code:

Ext.ux.grid.filter.MultiListFilter = Ext.extend(Ext.ux.grid.filter.Filter, {
getSerialArgs : function () {
        var args = {type: 'multilist', value: this.phpMode ? this.getValue().join(',') : this.getValue()};
        return args;
But when i declare a filter with type:"multilist" wher there was type:"list" i have an "not a constructor" error.

Am I missing something?