Adding parameter to render call when extending flask admin template

Question

I am trying to add content to a Flask-admin list view. I want to add my own content on top of the list view. What I have done so far is to extend the default list view and added my own content like so :

{% extends 'admin/model/list.html' %}

{% block body %}
    <h3>Submit report</h3>
    {% if report_form.errors %}
    <ul class="errors">
        {% for field_name, field_errors in report_form.errors|dictsort if field_errors %}
            {% for error in field_errors %}
                <li>{{ form[field_name].label }}: {{ error }}</li>
            {% endfor %}
        {% endfor %}
    </ul>
    {% endif %}
    <form action="{{ url_for('report.index') }}" method="post" enctype="multipart/form-data">
    {{ report_form.file }}
    {{ report_form.csrf_token }}
    <button type="submit">Send</button>
    </form>
    {{ super() }}
{% endblock %}

And my custom model view for this template is :

class ReportAdmin(ModelView):
    @expose('/', methods=('GET', 'POST'))
    def index(self):
        report_form = ReportFileForm()
        if form.validate_on_submit():
            file = form.file.data

            #Check for report duplicate
            if Report.query.filter(Report.filename == file.filename).all():
                flash('Could not add report because a report with filename {} already exists.'.format(file.filename), 'error')
            else:
                try:
                    report = parser_factory(file)
                    flash('Report was submitted succesfully')
                    return redirect(url_for('report.index_view'))
                except ValueError as e:
                    form.file.errors.append(e)

        return self.render('report/index.html', report_form=report_form)

Now my problem is that the list view expects a certain number of parameters to be set (to handle displaying the list).

Those parameters are defined inside base.py

return self.render(
            self.list_template,
            data=data,
            form=form,
            delete_form=delete_form,

            # List
            list_columns=self._list_columns,
            sortable_columns=self._sortable_columns,
            editable_columns=self.column_editable_list,

            # Pagination
            count=count,
            pager_url=pager_url,
            num_pages=num_pages,
            page=view_args.page,

            # Sorting
            sort_column=view_args.sort,
            sort_desc=view_args.sort_desc,
            sort_url=sort_url,

            # Search
            search_supported=self._search_supported,
            clear_search_url=clear_search_url,
            search=view_args.search,

            # Filters
            filters=self._filters,
            filter_groups=self._filter_groups,
            active_filters=view_args.filters,

            # Actions
            actions=actions,
            actions_confirmation=actions_confirmation,

            # Misc
            enumerate=enumerate,
            get_pk_value=self.get_pk_value,
            get_value=self.get_list_value,
            return_url=self._get_list_url(view_args),
        )

So of course when trying to display the page, I get an error :

jinja2.exceptions.UndefinedError: 'num_pages' is undefined

My question is : how do I include my parameter into the render call of the parent view?

Thanks!

Answer 1

Try overriding the view's render method where you will be able to inject your variables into the kwargs argument.

Example (untested)

class ReportAdmin(ModelView):

    list_template = 'report/index.html'

    #  Override to allow POSTS
    @expose('/', methods=('GET', 'POST'))
    def index_view(self):
        return super(ReportAdmin, self).index_view(self)

    def render(self, template, **kwargs):
        # we are only interested in our custom list page
        if template == 'report/index.html':

            report_form = ReportFileForm()
            if report_form.validate_on_submit():
                file = report_form.file.data

                #Check for report duplicate
                if Report.query.filter(Report.filename == file.filename).all():
                    flash('Could not add report because a report with filename {} already exists.'.format(file.filename), 'error')
                else:
                    try:
                        report = parser_factory(file)
                        flash('Report was submitted succesfully')
                    except ValueError as e:
                        report_form.file.errors.append(e)

            kwargs['report_form'] = report_form

        return super(ReportAdmin, self).render(template, **kwargs)