Flask-SQLAlchemy:模型字段的值由函数生成，并且在我重新启动应用程序之前保持不变

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///app.db'
db = SQLAlchemy(app)

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(50))
    email = db.Column(db.String(50))

    @property
    def generated_value(self):
        # 在这里编写生成字段值的函数逻辑
        return "Generated Value"

@app.route('/')
def index():
    user = User.query.first()
    return user.generated_value

if __name__ == '__main__':
    app.run()