Flask-SQLAlchemy导入/上下文问题

Question

我想构建我的Flask应用程序,例如:

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

apps.members 是一个Flask蓝图.

现在,为了创建模型类,我需要掌握应用程序,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我的Blueprint应用程序,我会感到害怕RuntimeError: working outside of request context.我怎样才能正确掌握我的应用程序？相对导入可能有效,但它们非常丑陋且有自己的上下文问题,例如:

from ...site import app

# ValueError: Attempted relative import beyond toplevel package

Answer 1

该flask_sqlalchemy模块不必立即使用应用程序进行初始化 - 您可以这样做:

# apps.members.models
from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()

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

然后在您的应用程序设置中,您可以致电init_app:

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

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

这样就可以避免周期性进口.

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:这是一个给你的一些功能的草图 - 显然你可以做更多的事情来使开发更容易(使用create_app模式,在某些文件夹中自动注册蓝图等)}

Answer 2

原来app.py:http://pythonhosted.org/Flask-SQLAlchemy/quickstart.html#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,上述答案不起作用.需要一个行代码才能工作.

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/