Cascading fields example

gistfile1.txt

ModelView
---------
# field1 (->Model1), field2 (->Model2) filtered by field1 values
    column_filter_by = ('field2')

    form_widget_args = {
        'field2': {
            'data-filter-by': 'field1',
        }
    }
    
    form_ajax_refs = {
        'field2': FilteredAjaxModelLoader(
            'field2', db.session, models.Model2,
            fields=('name',),
            page_size=10,
            placeholder='Choose',
            filter_by=(models.Model1, 'field1'),
        ),
    }

    @expose('/ajax/lookup/')
    def ajax_lookup(self):
        name = request.args.get('name')
        query = request.args.get('query')
        offset = request.args.get('offset', type=int)
        limit = request.args.get('limit', 10, type=int)
        # ---
        filter_by = request.args.get('filter_by')
        # ---

        loader = self._form_ajax_refs.get(name)

        if not loader:
            abort(404)

        # ---
        # for specific fields pass 'filter_by' parameter to add additional filter
        if name in self.column_filter_by:
            data = [loader.format(m) for m in loader.get_list(query, offset, limit, filter_by)]
        else:
        # ---
            data = [loader.format(m) for m in loader.get_list(query, offset, limit)]
        return Response(json.dumps(data), mimetype='application/json')

class FilteredAjaxModelLoader(QueryAjaxModelLoader):
    def get_list(self, term, offset=0, limit=DEFAULT_PAGE_SIZE, filter_by=None):
        query = self.session.query(self.model)

        # ---
        filter_by_options = self.options.get('filter_by')
        if filter_by_options and filter_by:
            filter_by = self.session.query(filter_by_options[0]).filter_by(
                id=filter_by).first()
            if filter_by:
                query = query.filter(getattr(self.model, filter_by_options[1])==filter_by)
        # ---

        filters = (field.ilike(u'%%%s%%' % term) for field in self._cached_fields)
        query = query.filter(or_(*filters))

        if self.order_by:
            query = query.order_by(self.order_by)

        return query.offset(offset).limit(limit).all()

templates/admin/lib.html
------------------------
<script src="{{ static('js/admin/form_custom.js') }}"></script>
# instead of form.js

form_custom.js
--------------
      function processAjaxWidget($el, name) {
        var multiple = $el.attr('data-multiple') == '1';
        // ---
        var filter_by = $el.attr('data-filter-by');
        // ---

        var opts = {
          width: 'resolve',
          minimumInputLength: 1,
          placeholder: 'data-placeholder',
          ajax: {
            url: $el.attr('data-url'),
            data: function(term, page) {
        // ---
              var result = {
                query: term,
                offset: (page - 1) * 10,
                limit: 10
              };
              if (filter_by) {
                result['filter_by'] = $('#' + filter_by).val();
              }
              return result;
        // ---
            },
...