Flask / Automatic Database field change on True depending on the date - flask

Question

How to make expired default in False and automatic setting of the expired to True, depending on whether the date has passed from the field expire_date?
My model.py
class PlanPurchase(db.Model):
plan_id = db.Column(db.Integer, db.ForeignKey('plan.plan_id'))
user_id = db.Column(db.Integer, db.ForeignKey('user.user_id', ondelete='CASCADE'))
expire_date = db.Column(db.DateTime)
expired = db.Column(db.Boolean)
def __init__(self, plan_id, user_id, expire_date, total_cost=0, expired=True):
self.plan_id = plan_id
self.user_id = user_id
self.expire_date = expire_date
self.expired = expired
Example.
expire_date = 2020-02-02 . expired should be True.
expire_date = 2020-12-12 . expired should be False.
It should be automatic. Compare current date and date in expire_date

Answer 1

There are two approaches for this.
If you have some kind of login system and user has to login to interact with PlanPurchase, then you can use before_request flask decorator to check for expiration and update the field. The before_requestcallback is always run before your actual endpoint request.
#app.before_request
def before_request_func():
if session.get('logged_in'):
""""
Check for expiration
and update expire field accordingly.
"""
#app.route("/login")
def login():
"""
Your login logic goes here.
"""
session['logged_in'] = True
You can use background task like celery or even configure cron jobs to check for expiration logic every midnight and update accordingly.
It depends upon your application architecture on which method you should use.
Tip:
Seems like you are using flask_sqlalchemy. You don't need the __init__ to pass parameters to the DB model. You can discard it.
class PlanPurchase(db.Model):
plan_id = db.Column(db.Integer, db.ForeignKey('plan.plan_id'))
user_id = db.Column(db.Integer, db.ForeignKey('user.user_id', ondelete='CASCADE'))
expire_date = db.Column(db.DateTime)
expired = db.Column(db.Boolean)
purhcase = PlanPurchase(plan_id=1,user_id=1,expired_date=datetime.now(),expired=False)
The above code works fine.