Process a topic name for basic forum app

[valenciano8]

Hi everyone !

I’m imporving my Django skills through a basic forum app.

Here are my templates files :

1. forums.html (Will show all of the Forum models)

2. topics.html (Will show all of the Topic models according to the Forum ForeignKey)

3. posts.html (Will show all of the related *post to a Topic)

I’ve got one issue in the topics.html template.
Indeed :

<tbody>

                {% for topic in topic_model %}

                <tr>
                    <td><a href="{{topic.topic_name}}">{{topic.topic_name}}</a></td>
                    <td>{{topic.topic_description}}</td>
                    <td>{{topic.topic_author}}</td>
                    <td>{{topic.topic_answers}}</td>
                    <td>{{topic.topic_last_answer_by}}</td>
                </tr>

                {% endfor %}

</tbody>

urls.py

from django.urls import path
from . import views

urlpatterns = [
    path("", views.index, name="index"),
    path("<str:forum_name>/", views.forum_page, name="forum_page"),
    path("topics/<str:topic_name>/", views.topic_page, name="topic_page")
]

My issue is that assuming we have a topic named “Hello World”, with the configuration above the URL will be :

localhost:8000/forums/topics/Hello World

and I would like to convert it as :

localhost:8000/forums/topics/hello-world

How can I process to implement the following function inside my template ? :

def processTopicName(topic_model):

    #Process topic name

    new_topic_model = []

    for topic in topic_model:

        topic_new_name = topic_name.replace(" ","-")
        topic_new_name = topic_new_name.lower()

        new_topic_model.append(topic_new_name)

    return topic_new_name 

Thank you in advance for your help

[KenWhitesell]

Perhaps you’re looking for the slugify feature?

Also, in django.utils.text there’s the slugify function.

Both of which will eventually lead you to reading SlugField and https://docs.djangoproject.com/en/3.0/ref/urls/#module-django.urls.conf

[timonweb]

I suggest using the AutoSlugField from the django-extensions package. It will do everything for you automatically, check docs here: https://django-extensions.readthedocs.io/en/latest/field_extensions.html#current-database-model-field-extensions

[valenciano8]

Hi guys ! Thanks ! Your solution did work !

Thus, I have one other request. How could I simplify my code ? Because I’d like to create a base class “Slugs” like so :

class Slugs():
    model_name_raw = models.CharField(max_length=40, default=None)
    model_name_slug = models.SlugField(max_length=80, default=None, blank=True)

    def save(self, *args, **kwargs):
        self.model_name_slug = slugify(self.model_name_raw)
        self.save(*args, **kwargs)

    def __str__(self):
        return self.model_name_raw

And then implement it via inheritance like :

class Forum(models.Model, Slugs):
    forum_description = models.CharField(max_length=100)

class Topic(models.Model, Slugs):
    topic_forum = models.ForeignKey(Forum, related_name="topic_forum", on_delete=models.CASCADE)
    topic_description = models.CharField(max_length=100)
    topic_author = models.ForeignKey(User, related_name="topic_author", on_delete=models.CASCADE)
    topic_answers = models.IntegerField(default=0)
    topic_last_answer_by = models.ForeignKey(User,related_name="topic_last_answer_by",on_delete=models.CASCADE)

Thank you in advance for your help

[timonweb]

I think you need an abstract class here. And the save method should call a super. So I would change Slugs to:

class ModelWithSlugs(models.Model):
    model_name_raw = models.CharField(max_length=40, default=None)
    model_name_slug = models.SlugField(max_length=80, default=None, blank=True)

    class Meta:
        abstract = True

    def save(self, *args, **kwargs):
        self.model_name_slug = slugify(self.model_name_raw)
        super().save(*args, **kwargs)

    def __str__(self):
        return self.model_name_raw

And then in your code:

class Forum(ModelWithSlugs):
    ...

class Topic(ModelWithSlugs):
   ....

Something like that…

[valenciano8]

Hi @timonweb !

Thank you for your answer, but it doesn’t really work (well, it is just that I don’t know how to resolve the following issue). When I try to

python manage.py makemigrations

I obtain :

You are trying to add a non-nullable field 'slugs_ptr' to forum without a default; we can't do that (the database needs something to populate existing rows)
Please select a fix: 
1) Provide a one-off default now (will be set on all existing rows with a null value for this column) 
2) Quit, and let me add a default in models.py

Here is my code updated :

class Slugs(models.Model):

    model_name_raw = models.CharField(max_length=40, default=None)

    model_name_slug = models.SlugField(max_length=80, default=None, blank=True)

    def save(self, *args, **kwargs):

        self.model_name_slug = slugify(self.model_name_raw)

        super().save(*args, **kwargs)

    def __str__(self):

        return self.model_name_raw

# Create your models here.

class Forum(Slugs):

    forum_description = models.CharField(max_length=100)

class Topic(Slugs):

    topic_forum = models.ForeignKey(Forum, related_name="topic_forum", on_delete=models.CASCADE)

    topic_description = models.CharField(max_length=100)

    topic_author = models.ForeignKey(User, related_name="topic_author", on_delete=models.CASCADE)

    topic_answers = models.IntegerField(default=0)

    topic_last_answer_by = models.ForeignKey(User,related_name="topic_last_answer_by",on_delete=models.CASCADE)

[KenWhitesell]

You missed the Meta definition of an abstract class that timonweb provided in his example of the Slugs class. Without it, it’s trying to create a table named Slugs along with an implicit foreign key field in the child classes. This is most likely not what you want.

    class Meta:
        abstract = True

[valenciano8]

Hi @KenWhitesell, thank you for your answer

Well it works now ! But is it a common Python thing to put an inside :

class Meta:
    abstract = True

Or a Django related thing ?

[timonweb]

It’s a Django related thing. By default, Django ORM assumes a database table for every class that extends models.Model, but if you don’t want this behaviour and want to use a class as a base without a table, you add abstract = True to its meta. More info here: https://docs.djangoproject.com/en/3.0/topics/db/models/#abstract-base-classes

[KenWhitesell]

In addition to @timonweb above, I’d also recommend looking at the rest of the options available in the Meta class available for models. (Also see Model Meta options.)