Hi Alessandro,

It happened because the root validator was designed to slugify the title and ignore the actual slug that we are sending.

We did not take into consideration if we are sending a slug value. To take it into consideration we need to modify values["slug"] = values.get("title").replace(" ","-").lower()

@root_validator(pre=True)
def generate_slug(cls, values):
    if 'title' in values:
        values["slug"] = values.get("slug") or values.get("title").replace(" ","-").lower()
        return values

By doing this change, we are giving first preference to the slug value being sent. If the slug value is not there, we will slugify the title and use it.

Hi Sourabh, I think I got the reason why this is happening.

The responsibility is not on the UpdateBlog Pydantic model, which is indeed correctly inheriting the @root_validator, but rather in the implementation of the update_blog_by_id  function defined in the repository folder.

def update_blog_by_id(id: int, blog: UpdateBlog, db: Session, author_id: int = 1):
   blog_in_db = db.query(Blog).filter(Blog.id == id).first()
   if not blog_in_db:
       ...
   if not blog_in_db.author_id == author_id:
       ...
   blog_in_db.title = blog.title
   blog_in_db.content = blog.content
   db.add(blog_in_db)
   db.commit()
   return blog_in_db

As such, the slug field does not get any update in the db. We should add blog_in_db.slug = blog.slug  to make it work.