django-filter: order_by に複数指定可能にする

• alex/django-filter (doc)
• ソート条件を複数指定できるようにする

/events?o=opening_on&o=-title
/events?o=-presenter&o=-opening_on&o=title

順序フィルター: OrderingFilter

class EventFilter(django_filters.FilterSet):
    # https://github.com/carltongibson/django-filter/blob/develop/docs/migration.txt
    o = django_filters.OrderingFilter(
        choices=(
            ('-opening_on', _('Opening On Desc')),
            ('opening_on', _('Openning On Asc')),
            ('-title', _('Title Desc')),
            ('title', _('Title Asc')),
            ('presenter', _('Presenter Asc')),
            ('-presenter', _('Presenter Desc')), ))

    class Meta:
        model = models.Event

テンプレートタグ: ordering

• query でクエリ文字列を返す
• direction に asc / desc を返す

@register.assignment_tag(takes_context=True)                                        
def ordering(context, field, key='o'):                                              
    qdict = context.get('request').GET.copy()                                              
    rfield = '-' + field                                                            
    q = qdict.getlist(key)                                                            
    if rfield in q:                                                                 
        q.remove(rfield)                                                            
        direction = "asc"                                                           
    else:                                                                           
        if field in q:                                                              
            q.remove(field)                                                         
        field = rfield                                                              
        direction = "desc"                                                          

    q = [field] + q                                                                 
    qdict.setlist(key, q)                                                             
    return dict(query=qdict.urlencode(), direction=direction)   

テンプレート:

{% load mytags %}

<thead>
  <tr>
    <th>
      {% ordering 'opening_on' as opening_on_order %}
      <a href="?{{ opening_on_order.query }}">
        <span class="sort-{{ opening_on_order.direction }}">{% trans 'Opening On' %}</span></a></th>

    <th>
      {% ordering 'title' as title_order %}
      <a href="?{{ title_order.query }}">
        <span class="sort-{{ title_order.direction }}">{% trans 'Event Title' %}</span></a></th>
  </tr>
</thead>

スタイル:

<style>
.sort-asc:after{content: "↓"}
.sort-desc:after{content: "↑"}
</style>