如何以及在何处删除 Flask - SQLAlchemy 中的行

Question

I'm building a project using flask and flask-SQLAlchemy (with sqlite3 and with python 3.8). I have models.py which holds all the tables of the db, and I want to have static method which deletes rows in Articles table depends on one of their attribute.

I thought about writing this funciton in the models class and wanted to ask if that's fine. The function looks like:

def update_articles():
    all_articles = Articles.query.all()
    for article in all_articles:
        if needs_to_be_deleted(article):
            db.session.delete(article)
            db.session.commit()

Is that funciton fine (don't mind the needs_to_be_deleted(article) thing). Is the way I delete the article good? and is the place for this function can be at the models.py file?

Answer 1

As per my experience its all good here. As a general rule you should design your application as:

1. Models should do the most powerful stuff
2. Views should carry out only logical work
3. Templates should be dumb. They should just render things.

Now by saying the above i mean to say all the stuff relating to the operations with database should be in the models. Just like you are doing. Most of the time all the transactions with your database are simple ones and can be written with a couple of lines with ORM. But sometimes if you feel that something needs to be done over and over again or you feel like having a method for doing something big. Then its better to have that in your models only. The method you mentioned should be a part of your Article model. Other things that can be there in your model could be operations like sending emails to users or some other routine tasks.

As far as your views are concerned. They should carry out all the logical stuff. Your business logic is basically implemented by the views.

Lastly templates should do the work of rendering things whatever is fed to them by the views.

Obviously there are no such hard and fast rule. There can be exceptions to the above. Or someone could find any other way of doing things better rather than that i mentioned. For that you need to use your own conscience and no one can teach you that. It comes with experience.

For your reference please go through the following articles:

https://blog.miguelgrinberg.com/post/the-flask-mega-tutorial-part-i-hello-world

https://flask.palletsprojects.com/en/1.1.x/tutorial/

Also you might be using this but in case your aren't: https://flask-marshmallow.readthedocs.io/en/latest/

Just one small suggestion too. though i am not clear about your requirements. But it would be better if you could commit after the for loop ie at the very end of the method. A request should generally have only one commit.