Django Haystack Mixin to make templates obsolete

auto_prepare_text_index_mixin.py

class AutoPrepareTextIndexMixin(object):
    """
    Used with Indexed Classes to add common functions:
    1. Prepares text to be documented using fields from the list document_fields
    2. Gets fields to be `select_related` for efficient db querying while indexing
    3. Defines "get_updated_field"
    Also tries to check for these modifications and raises errors if things not implemented like they should be
    """

    def __init__(self):
        super(AutoPrepareTextIndexMixin, self).__init__()
        default_pk_field = getattr(settings, 'HAYSTACK_ADMIN_DEFAULT_ORDER_BY_FIELD', None)
        if default_pk_field:
            if default_pk_field not in self.fields.keys():
                raise NotImplementedError('Need a field for "{0}" in {1} like so "{0} = indexes.'
                                          'IntegerField(model_attr=\'pk\')"'.format(default_pk_field, self.__class__))

        if self.get_content_field() != 'text':
            raise NameError('The content field should be named "text" in {} or it wont be '
                            'prepared like we want it to'.format(self.__class__))

        document_fields = getattr(self, 'document_fields', None)
        if not document_fields:
            raise NotImplementedError('"document_fields" not specified for {}, what am I going to put in '
                                      'the document brah?'.format(self.__class__))

    def get_updated_field(self):
        return 'updated_at'

    def index_queryset(self, using=None):
        select_related_for_index = getattr(self, 'select_related_for_index', None)
        if select_related_for_index:
            return self.get_model().objects.select_related(*self.select_related_for_index)
        else:
            return self.get_model().objects.all()

    def prepare_text(self, obj):
        document_fields = getattr(self, 'document_fields', None)

        values = []
        for field in document_fields:
            full_field_list = field.split('__')
            field_value = reduce(lambda acc_attr, attr: getattr(acc_attr, attr), full_field_list, obj)
            values.append(field_value)

        return ' '.join(map(unicode, values))