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Flask-SQLAlchemy导入/上下文问题

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问题：Flask-SQLAlchemy导入/上下文问题
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问题：Flask-SQLAlchemy导入/上下文问题

我想构建我的Flask应用，例如：

./site.py
./apps/members/__init__.py
./apps/members/models.py

apps.members 是烧瓶蓝图。

现在，为了创建模型类，我需要拥有该应用程序，例如：

# apps.members.models
from flask import current_app
from flaskext.sqlalchemy import SQLAlchemy

db = SQLAlchemy(current_app)

class Member(db.Model):
    # fields here
    pass

但是，如果我尝试将该模型导入到我的Blueprint应用程序中，则会感到恐惧RuntimeError: working outside of request context。我如何在这里正确持有我的应用程序？相对导入可能有效，但它们很丑陋，并且有自己的上下文问题，例如：

from ...site import app

# ValueError: Attempted relative import beyond toplevel package
点击查看英文原文

I want to structure my Flask app something like:

./site.py
./apps/members/__init__.py
./apps/members/models.py

apps.members is a Flask Blueprint.

Now, in order to create the model classes I need to have a hold of the app, something like:

# apps.members.models
from flask import current_app
from flaskext.sqlalchemy import SQLAlchemy

db = SQLAlchemy(current_app)

class Member(db.Model):
    # fields here
    pass

But if I try and import that model into my Blueprint app, I get the dreaded RuntimeError: working outside of request context. How can I get a hold of my app correctly here? Relative imports might work but they’re pretty ugly and have their own context issues, e.g:

from ...site import app

# ValueError: Attempted relative import beyond toplevel package

回答 0

该flask_sqlalchemy模块没有要与应用程序马上初始化-你可以这样做，而不是：

# apps.members.models
from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()

class Member(db.Model):
    # fields here
    pass

然后在应用程序设置中，您可以调用init_app：

# apps.application.py
from flask import Flask
from apps.members.models import db

app = Flask(__name__)
# later on
db.init_app(app)

这样可以避免周期性导入。

这种模式并没有必要在你把你所有的车型在一个文件中。只需将db变量导入每个模型模块即可。

例

# apps.shared.models
from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()

# apps.members.models
from apps.shared.models import db

class Member(db.Model):
    # TODO: Implement this.
    pass

# apps.reporting.members
from flask import render_template
from apps.members.models import Member

def report_on_members():
    # TODO: Actually use arguments
    members = Member.filter(1==1).all()
    return render_template("report.html", members=members)

# apps.reporting.routes
from flask import Blueprint
from apps.reporting.members import report_on_members

reporting = Blueprint("reporting", __name__)

reporting.route("/member-report", methods=["GET","POST"])(report_on_members)

# apps.application
from flask import Flask
from apps.shared import db
from apps.reporting.routes import reporting

app = Flask(__name__)
db.init_app(app)
app.register_blueprint(reporting)

注意：这是一些功能的草图 -显然，您可以做很多事来简化开发工作（使用create_app模式，在某些文件夹中自动注册蓝图等）。

点击查看英文原文

The flask_sqlalchemy module does not have to be initialized with the app right away – you can do this instead:

# apps.members.models
from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()

class Member(db.Model):
    # fields here
    pass

And then in your application setup you can call init_app:

# apps.application.py
from flask import Flask
from apps.members.models import db

app = Flask(__name__)
# later on
db.init_app(app)

This way you can avoid cyclical imports.

This pattern does not necessitate the you place all of your models in one file. Simply import the db variable into each of your model modules.

Example

# apps.shared.models
from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()


# apps.members.models
from apps.shared.models import db

class Member(db.Model):
    # TODO: Implement this.
    pass


# apps.reporting.members
from flask import render_template
from apps.members.models import Member

def report_on_members():
    # TODO: Actually use arguments
    members = Member.filter(1==1).all()
    return render_template("report.html", members=members)


# apps.reporting.routes
from flask import Blueprint
from apps.reporting.members import report_on_members

reporting = Blueprint("reporting", __name__)

reporting.route("/member-report", methods=["GET","POST"])(report_on_members)


# apps.application
from flask import Flask
from apps.shared import db
from apps.reporting.routes import reporting

app = Flask(__name__)
db.init_app(app)
app.register_blueprint(reporting)

Note: this is a sketch of some of the power this gives you – there is obviously quite a bit more that you can do to make development even easier (using a create_app pattern, auto-registering blueprints in certain folders, etc.)

回答 1

原来app.py：https://flask-sqlalchemy.palletsprojects.com/en/2.x/quickstart/

...

app = flask.Flask(__name__)
app.config['DEBUG'] = True
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:////tmp/test.db'
db = flask.ext.sqlalchemy.SQLAlchemy(app)

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

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

# Create the database tables.
db.create_all()

...

# start the flask loop
app.run()

我只是将一个app.py拆分为app.py和model.py而不使用Blueprint。在这种情况下，以上答案无效。需要行代码才能工作。

之前：

db.init_app(app)

之后：

db.app = app
db.init_app(app)

并且，以下链接非常有用。

http://piotr.banaszkiewicz.org/blog/2012/06/29/flask-sqlalchemy-init_app/

点击查看英文原文

an original app.py: https://flask-sqlalchemy.palletsprojects.com/en/2.x/quickstart/

...

app = flask.Flask(__name__)
app.config['DEBUG'] = True
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:////tmp/test.db'
db = flask.ext.sqlalchemy.SQLAlchemy(app)

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

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

# Create the database tables.
db.create_all()

...

# start the flask loop
app.run()

I just splitted one app.py to app.py and model.py without using Blueprint. In that case, the above answer dosen’t work. A line code is needed to work.

before:

db.init_app(app)

after:

db.app = app
db.init_app(app)

And, the following link is very useful.

http://piotr.banaszkiewicz.org/blog/2012/06/29/flask-sqlalchemy-init_app/