Remember form data for pagination

Question

In my Flask application, I have a view which renders a table of items by using the Flask-SQLAlchemy pagination method. Great stuff so far. But I want to add sorting and filtering, so I created a form with selectboxes where the user can choose the sort and filter options.

When submitting the sort/filter on the page, the view works fine: the first page is sorted. But selecting another page on the page, the pagination is falling back to the original query. What should I do to save my sort/filter options during new page loads? Using flask.g has come up to me, but is it the correct way?

class ItemTableForm(Form):
    sort_choices = [('id', 'ID'),
                    ('name', 'Name'),
                    ('status', 'Status')]
    filter_choices = [('all', 'All'),
                      ('instock', 'In stock'),
                      ('sold', 'Sold')]
    sort = SelectField(u'Sort by', choices=sort_choices)
    filter = SelectField(u'Filter by', choices=filter_choices)

@app.route('/browse/<int:page>', methods=("GET", "POST"))
def browse(page):
    form = ItemTableForm()
    if form.validate_on_submit():
        query = Item.query.order_by(getattr(Item, form.sort.data))
    else:
        query = Item.query

    pagination = paginate(query, page)
    return render_template('browse.html', pagination=pagination, form=form)

# My template contains this form and a regular HTML table
<form action="{{ url_for('browse') }}" method="POST">
  {{ form.hidden_tag() }}
  {{ form.sort.label }} {{ form.sort() }}
  {{ form.filter.label }} {{ form.filter() }}
  <button type="submit" class="btn">Submit</button>
</form>

Answer 1

You can use url parameters to pass the info about sorting. Say user selects sorting by name. Then add this at the end of url

    your_url?sort=name

Then you can access it as

    value = request.args.get('name','')

Simply pass sorting variable value to the template where you append sort value to the next url.

Edit:

To create such url in Flask, do this:

    url_for('url_view_name', sort='name')

This will return the url with sort appended as query argument. Check out the flask documentation here to know more about url building