Flask-SQLAlchemy：如何在模型实例提交到数据库之前调用实例方法？

Question

我有一个想要初始化的模型，例如SomeModel(name='george', password='whatever').

在将它提交到数据库之前，我想调用另一个方法（我们称之为gen_password_hash）来创建密码的哈希版本，并将其设置为模型实例的属性。

所以我希望这发生在实例化之后，但在提交到数据库之前。

更新

我想看看是否可以通过在我的模型上定义 __init__ 函数来实现这一点。

def __init__(self, **kwargs):
    self.set_pass(kwargs.pop('password'))
    super(User, self).__init__(**kwargs)
    self.generate_email_address_confirmation_token()

这是我在尝试删除/重新创建表以重置我的应用程序时得到的回溯：

Traceback (most recent call last):
  File "main.py", line 7, in <module>
    import gg.cli
  File "/home/blaine/freelance/myproject/gg/cli/__init__.py", line 183, in <module>
    reset_all()
  File "/home/blaine/freelance/myproject/gg/cli/__init__.py", line 164, in reset_all
    load_test_data()
  File "/home/blaine/freelance/myproject/gg/cli/__init__.py", line 51, in load_test_data
    admin=True)
  File "<string>", line 4, in __init__
  File "/home/blaine/freelance/myproject/lib/python3.4/site-packages/sqlalchemy/orm/state.py", line 414, in _initialize_instance
    manager.dispatch.init_failure(self, args, kwargs)
  File "/home/blaine/freelance/myproject/lib/python3.4/site-packages/sqlalchemy/util/langhelpers.py", line 66, in __exit__
    compat.reraise(exc_type, exc_value, exc_tb)
  File "/home/blaine/freelance/myproject/lib/python3.4/site-packages/sqlalchemy/util/compat.py", line 187, in reraise
    raise value
  File "/home/blaine/freelance/myproject/lib/python3.4/site-packages/sqlalchemy/orm/state.py", line 411, in _initialize_instance
    return manager.original_init(*mixed[1:], **kwargs)
  File "/home/blaine/freelance/myproject/gg/users.py", line 67, in __init__
    self.generate_email_address_confirmation_token()
  File "/home/blaine/freelance/myproject/gg/users.py", line 71, in generate_email_address_confirmation_token
    token.update(self.email_address.encode() + current_app.secret_key + \
  File "/home/blaine/freelance/myproject/lib/python3.4/site-packages/werkzeug/local.py", line 347, in __getattr__
    return getattr(self._get_current_object(), name)
  File "/home/blaine/freelance/myproject/lib/python3.4/site-packages/werkzeug/local.py", line 306, in _get_current_object
    return self.__local()
  File "/home/blaine/freelance/myproject/lib/python3.4/site-packages/flask/globals.py", line 51, in _find_app
    raise RuntimeError(_app_ctx_err_msg)
RuntimeError: Working outside of application context.

This typically means that you attempted to use functionality that needed
to interface with the current application object in a way.  To solve
this set up an application context with app.app_context().  See the
documentation for more information.

我用this question for reference。

Answer 1

以下是我对您要做什么的解释。您想创建一个静态方法，将给定的字符串密码转换为散列密码。显然python的hash不是密码散列函数，所以我建议使用其他更一致和可靠的东西。在您的应用程序中初始化User 模型期间可以使用这种散列方法。这意味着每次您使用用户名、电子邮件和密码创建用户时，该密码在成为随后的User 对象的属性之前首先被散列。请看以下示例：

from flask import Flask
from flask_sqlalchemy import SQLAlchemy


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


class User(db.Model):
    __tablename__ = 'users'

    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(80), unique=True)
    email = db.Column(db.String(120), unique=True)
    password = db.Column(db.String(36))

    def __init__(self, username, email, password):
        self.username = username
        self.email = email
        self.password = self.generate_pwd_hash(password)

    @staticmethod
    def generate_pwd_hash(pwd):
        """
        This is where you define how
        to hash the user's password.
        """
        return str(hash(pwd))  # This is, of course, not the way to hash a password


db.create_all()

user = User(username='george',
            email='george@example.com',
            password='whatever')

try:
    db.session.add(user)
    db.session.commit()
except:
    print("This username must already exist.")