Cfrgtkky

I use Django 1.11 and the parler plugin for translation. Every time I save a slug, I wish to

• test if it already exists


• truncate the slug


• add number


• test again, if the new slug exists and so on

This way, I wish to create a unique slug on saving.

models.py:

from parler.models import TranslatableModel

from django.utils.translation import gettext_lazy as _



class Event(TranslatableModel):

    translations = TranslatedFields(

        event_title=models.CharField(_("event title"), max_length=512),

        slug=models.SlugField(_("slug"), help_text=_("Used in the URL of the event page.")),

        description=RichTextUploadingField(blank=True),

        meta={'unique_together': (('language_code', 'slug'),)},

    )



    def save_translation(self, translation, *args, **kwargs):

        """Create a unique slug of 45 Characters + a dash and 4 digits."""

        translation.slug = translation.slug[:50]

        if Event.objects.active_translations(slug=translation.slug).exists():

            # This is true on the first test for no apparent reason.

            i = 0

            while Event.objects.active_translations(slug=translation.slug).exists():

                translation.slug = translation.slug[:44]+'-'+str(i)

                i += 1

        super(Event, self).save_translation(translation, *args, **kwargs)

This code dosen't work. It always add a number to the slug, no matter what, even if I enter a completely new slug.

The problem here is that save_translation gets called multiple times. My solution is:

def save_translation(self, translation, *args, **kwargs):

    """Create a unique slug build of the title + language code + a number."""

    translation.slug = translation.slug[:50]

    """

    This filter is a bit more complicated.

    If the same slug but with a differen ID alread exists:

        ~Q(id=translation.master_id) & 

        Q(translations__slug=translation.slug)

    Or if the same slug with the same ID but different language already exists:

        Q(id=translation.master_id) & 

        ~Q(translations__language_code=translation.language_code) & 

        Q(translations__slug=translation.slug)

    """

    if Event.objects.filter(

            (~Q(id=translation.master_id) &

             Q(translations__slug=translation.slug)) |

            (Q(id=translation.master_id) &

             ~Q(translations__language_code=translation.language_code) &

             Q(translations__slug=translation.slug))

    ).exists():

        i = 1

        while Event.objects.filter(

                (~Q(id=translation.master_id) &

                 Q(translations__slug=translation.slug)) |

                (Q(id=translation.master_id) &

                 ~Q(translations__language_code=translation.language_code) &

                 Q(translations__slug=translation.slug))

        ).exists():

            # Truncate the slug, if it is too long. This happens, if the

            # initial slug is to long or if the trailing number reaches

            # another digit.

            trunc_number = (4 + ceil(log10(i + 1)))

            if len(translation.slug) + trunc_number > 50:

                translation.slug = translation.slug[:50-trunc_number]



            # Substitute the trailing language code and number with a bigger number.

            translation.slug = re.sub(

                r'(?P<slug_start>.*?)(-(de|en))?(-(d)+)?$',

                'g<slug_start>' + '-' + translation.language_code + '-' + str(i),

                translation.slug)

            i += 1

    super(Event, self).save_translation(translation, *args, **kwargs)

It got a bit longer then I hoped, but I think it works.