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用户加载器与 UserMixin

配置 LoginManager 和用户模型

第 2 / 4 课13 个步骤

用户加载器与 UserMixin 是 CoddyKit 上的免费 Flask Academy 课时。这是第 2 节课，共 4 节。你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。这是 Flask Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Flask Academy 课程共包含 4 节课。

本课时的部分内容尚未翻译，以英文显示。

Meet Flask-Login

The Flask-Login extension manages who is logged in for you. It tracks the current user across requests so you do not wire sessions by hand.

pip install flask-login

Create a LoginManager

Everything starts with a LoginManager. You create one instance and connect it to your app so Flask-Login can hook into requests.

from flask_login import LoginManager
login_manager = LoginManager()
login_manager.init_app(app)

It Needs Two Things

To work, the manager needs a user model that follows its rules and a function that loads a user by id. Today you set up both.

The UserMixin Shortcut

Your model must expose a few properties like is_authenticated. The UserMixin class supplies them all, so you just inherit from it.

from flask_login import UserMixin
class User(UserMixin, db.Model):
    id = db.Column(db.Integer, primary_key=True)

What UserMixin Gives You

UserMixin adds is_authenticated, is_active, is_anonymous, and get_id for free. That last one returns your user id as a string.

The user_loader Callback

Flask-Login stores only the user id in the session. It calls your user_loader on each request to turn that id back into a real user.

Register the Loader

Decorate a function with login_manager.user_loader. It receives the id from the session and must return a user object or None.

@login_manager.user_loader
def load_user(user_id):
    return User.query.get(int(user_id))

Ids Arrive as Strings

The id passed to your loader is always a string, since it came from a cookie. Cast it to int before querying an integer primary key.

return User.query.get(int(user_id))

Return None for Unknowns

If the id matches no row, your loader should return None. Flask-Login then treats the request as coming from an anonymous visitor.

Override get_id If Needed

If your primary key is not named id, override get_id so it returns the right value. Most apps with a plain id column never touch it.

def get_id(self):
    return str(self.uuid)

Pieces Now Connected

With the manager, the UserMixin model, and a user_loader in place, Flask-Login can identify the current user on every incoming request.

Quick Check

Think about what the session actually stores between requests.

在交互式课程中回答

Recap

You wired a LoginManager, mixed UserMixin into your model, and wrote a user_loader. Flask-Login can now rebuild the current user from a session. 👤

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常见问题解答

「用户加载器与 UserMixin」课时是免费的吗？

是的 — 「用户加载器与 UserMixin」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Flask Academy 课程的其余内容，请升级到 CoddyKit PRO。 Flask Academy 课程共包含 4 节课。

「用户加载器与 UserMixin」这节课中我会学到什么？

配置 LoginManager 和用户模型你通过在浏览器中直接运行的动手代码来练习 Flask Academy，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 Flask Academy 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Flask Academy 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。这是第 2 节课，共 4 节。

「用户加载器与 UserMixin」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

我能在这节 Flask Academy 课中编写并运行代码吗？

能。每节 Flask Academy 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

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