Python Flask 应用程序中的邮箱组件无法访问应用程序工厂模式中的应用程序实例

我在练习Flask .我已经做了一个简单的Flask 应用程序，它发送一封邮箱给管理员，说"新用户已加入."一旦有人输入他们的名字并在表单上提交.

这是邮箱组件:

from flask import current_app, render_template
from flask_mail import Message
from threading import Thread
from app import mail


# Send aync email functions
def send_aysnc_email(app, msg):
    with app.app_context():
        mail.send(msg)


def send_mail(to, subject, template, **kwargs):
    app = current_app
    msg = Message(
        app.config["FLASKY_MAIL_SUBJECT_PREFIX"] + subject,
        sender=app.config["FLASKY_MAIL_SENDER"],
        recipients=[to],
    )

    msg.body = render_template(template + ".txt", **kwargs)
    msg.html = render_template(template + ".html", **kwargs)
    thr = Thread(target=send_aysnc_email, args=[app, msg])
    thr.start()
    return thr

当我运行这款应用程序，在表格上输入姓名并按下提交时，邮箱不会被发送.

我在日志(log)上看到一个错误，说

Exception in thread Thread-3 (send_aysnc_email):
Traceback (most recent call last):
  File "/usr/lib/python3.10/threading.py", line 1016, in _bootstrap_inner
127.0.0.1 - - [02/Sep/2023 14:39:29] "POST / HTTP/1.1" 302 -
    self.run()
  File "/usr/lib/python3.10/threading.py", line 953, in run
    self._target(*self._args, **self._kwargs)
  File "/home/cadbay53/Desktop/practice/flask/app/emails.py", line 9, in send_aysnc_email
    with app.app_context():
  File "/home/cadbay53/Desktop/practice/flask/venv/lib/python3.10/site-packages/werkzeug/local.py", line 311, in __get__
    obj = instance._get_current_object()
  File "/home/cadbay53/Desktop/practice/flask/venv/lib/python3.10/site-packages/werkzeug/local.py", line 508, in _get_current_object
    raise RuntimeError(unbound_message) from None
RuntimeError: Working outside of application context.

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

我已经找到了解决这个问题的方法，但我不明白为什么当前的代码不起作用.

这是我的应用程序工厂:

from flask import Flask, render_template
from flask_bootstrap import Bootstrap
from flask_mail import Mail
from flask_moment import Moment
from flask_sqlalchemy import SQLAlchemy
from config import config

bootstrap = Bootstrap()
mail = Mail()
moment = Moment()
db = SQLAlchemy()


def create_app(config_name):
    app = Flask(__name__)
    app.config.from_object(config[config_name])
    config[config_name].init_app(app)

    bootstrap.init_app(app)
    mail.init_app(app)
    moment.init_app(app)
    db.init_app(app)

    from .main import main as main_blueprint

    app.register_blueprint(main_blueprint)

    return app

这是我创建应用程序的文件实例:

import os
from app import create_app
from app.models import User, Role
from flask_migrate import Migrate
from app import db

app = create_app("default")
migrate = Migrate(app, db)


@app.shell_context_processor
def make_shell_context():
    return dict(db=db, User=User, Role=Role)


@app.cli.command()
def test():
    """Run unit tests."""
    import unittest

    tests = unittest.TestLoader().discover("tests")
    unittest.TextTestRunner(verbosity=2).run(tests)

以下是配置:

import os

basedir = os.path.abspath(os.path.dirname(__file__))


class Config:
    SECRET_KEY = "***"
    MAIL_SERVER = "smtp.gmail.com"
    MAIL_PORT = 587
    MAIL_USE_TLS = True
    MAIL_USERNAME = "***@***.com"
    MAIL_PASSWORD = "****"
    FLASKY_MAIL_SUBJECT_PREFIX = "[Flasky]"
    FLASKY_MAIL_SENDER = "Flasky Admin <***@***.com>"
    FLASKY_ADMIN = "***@***.com"
    SQLALCHEMY_TRACK_MODIFICATIONS = False

    @staticmethod
    def init_app(app):
        pass


class DevelopmentConfig(Config):
    DEBUG = True
    SQLALCHEMY_DATABASE_URI = "sqlite:///" + os.path.join(basedir, "data-dev.sqlite")


class TestConfig(Config):
    TESTING = True
    SQLALCHEMY_DATABASE_URI = "sqlite:///"


class ProductionConfig(Config):
    SQLALCHEMY_DATABASE_URI = "sqlite:///" + os.path.join(basedir, "data.sqlite")


config = {
    "development": DevelopmentConfig,
    "testing": TestConfig,
    "production": ProductionConfig,
    "default": DevelopmentConfig,
}

以下是我的工作内容:

# Send aync email functions
def send_aysnc_email(app, msg):
    with app.app_context():
        mail.send(msg)


def send_mail(to, subject, template, **kwargs):
    app = current_app._get_current_object()
    msg = Message(
        app.config["FLASKY_MAIL_SUBJECT_PREFIX"] + subject,
        sender=app.config["FLASKY_MAIL_SENDER"],
        recipients=[to],
    )

    msg.body = render_template(template + ".txt", **kwargs)
    msg.html = render_template(template + ".html", **kwargs)
    thr = Thread(target=send_aysnc_email, args=[app, msg])
    thr.start()
    return thr

我不明白为什么app.app_context()不能访问当前的应用程序实例，而将当前的应用程序作为参数提供，并且可以很好地与current_app._get_current_object()一起工作.