Routablepage of the BlogPage/category - django-models

Question

I fail to display the routable index page for categories/given category.
My code uses:
-BlogCategory(model)
-BlogPageBlogCategory (page) an intemediary structure that links to:
-PostPage(page)
I can pass the code to the post_page template, but when I click on a specific category link I get:
Reverse for 'post_by_category' with arguments '('',)' not found. 1 pattern(s) tried: ['category/(?P<category>[-\\w]+)/$']
In the following post #gasman wrote: "the routablepageurl tag has received an empty string". I couldn't find the 'empty' string/missing link.
I assume it's related to the route of my 'def post_by_category'. Any input that would help me deepen my learning woulg be great.
NB - in case it helps, when I run this procedure without the intemeiary page all's fine. I can display the BlogPage/given_category once I click on the category in the PostPage.
Here's my code:
Models
class BlogPage(RoutablePageMixin, Page):
...
def get_context(self, request, *args, **kwargs):
context = super().get_context(request, *args, **kwargs)
context["posts"] = posts
return context
def get_posts(self):
return PostPage.objects.descendant_of(self).live().order_by("-post_date")
#route(r'^category/(?P<category>[-\w]+)/$')
def post_by_category(self, request, category, *args, **kwargs):
self.posts = self.get_posts().filter(categories__blog_category__slug=category)
context["categories"] = BlogCategory.objects.all()
return self.render(request)
class PostPage(MetadataPageMixin, Page):
...
content_panels = Page.content_panels + [
...
InlinePanel("categories", label="category"),
...
def get_context(self, request, *args, **kwargs):
context = super().get_context(request, *args, **kwargs)
return context
class PostPageBlogCategory(models.Model):
page = ParentalKey(
"blog.PostPage", on_delete=models.CASCADE, related_name="categories"
)
blog_category = models.ForeignKey(
"blog.BlogCategory", on_delete=models.CASCADE, related_name="post_pages"
)
panels = [
SnippetChooserPanel("blog_category"),
]
class Meta:
unique_together = ("page", "blog_category")
#register_snippet
class BlogCategory(models.Model):
name = models.CharField(max_length=255)
slug = models.SlugField(unique=True, max_length=80)
panels = [
FieldPanel('name'),
FieldPanel("slug"),
]
def __str__(self):
return self.name
class Meta:
verbose_name_plural = 'categories'
The post_page.html:
{% extends "base.html" %}
{% load wagtailroutablepage_tags %}
...
{% for category in page.categories.all %}
<li>
<a href="{% routablepageurl blog_page "post_by_category" category.slug %}">
{{ blog_category.name }}
</a>
</li>
{% empty %}
No categories yet'
{% endfor %}
...

Answer 1

After debugging and testing, I didn't find any blank categories, (which doesn't mean there were none, but that I didn't find or deleted them Unintentionally).
I case it could help, what worked for me was adding the category_type at the beginning of my varaiable:
{{ category.blog_category.name }} rather than {{ blog_category.name }}
{% for category in page.categories.all %}
<a href="{% routablepageurl article_index_page "post_by_category" category.blog_category.slug %}" class="link-primary text-decoration-none">
{{ category.blog_category.name }}
</a>
{% empty %}
No categories yet'
{% endfor %}