Avoid DetachedInstanceError in Flask-SQLAlchemy

gistfile1.py

# The following produces DetachedInstanceError

app = Flask(__name__)
db = SQLAlchemy(app)

class Foo(db.Model):
    id = db.Column(db.Integer, primary_key=True)
  
foo = Foo()
db.session.add(foo)
db.session.commit()
foo.id

>>> DetachedInstanceError: Instance <Foo at 0x10741ac10> is not bound to a Session; attribute refresh operation cannot proceed

# The following removes DetachedInstanceError

app = Flask(__name__)
db = SQLAlchemy(app, session_options{
    'expire_on_commit': False
})

class Foo(db.Model):
    id = db.Column(db.Integer, primary_key=True)
  
foo = Foo()
db.session.add(foo)
db.session.commit()
foo.id

>>> 1

Thank you for sharing. How do you run Flask? Uwsgi? Multi-thread? Multi-process?

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

# The following produces DetachedInstanceError

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///test.db'
app.config["SQLALCHEMY_TRACK_MODIFICATIONS"] = False
db = SQLAlchemy(app)
# db = SQLAlchemy(app, session_options={
#     'expire_on_commit': False
# })

class Foo(db.Model):
    id = db.Column(db.Integer, primary_key=True)

db.create_all()
foo = Foo()
db.session.add(foo)
db.session.commit()
print(foo.id)

I have ran the above code on my computer, but it didn't raise a DetachedInstanceError，the flask version on my computer is:

Flask==0.12
Flask-SQLAlchemy==2.2
SQLAlchemy==1.1.6

I have troubleshooting this issue half day, this is realy help me.
thank you very much！

Thank you very much help. This helped to solve my problem.