避免将应用程序工厂导入需要应用程序上下文的模块中 [英] Avoiding importing application factory into module needing application context

问题描述

这个问题是我上一个此处的扩展.建议我多解释一下这个问题.如标题所述，我正在尝试寻找一种避免将应用程序工厂(create_app函数)导入需要应用程序上下文并将current_app作为应用程序导入"的模块的方法.还不够.

This question is an extension on my previous one here. I was suggested to put more to explain the problem. As the heading says, I am trying to find a way to avoid importing the application factory (create_app function) into a module that needs application context and were "import current_app as app" is not sufficient.

我的问题是由于此 create_app 函数需要循环传递才能获取app_context，因此我遇到了循环导入问题.

My problem is I have a circular import problem due to this create_app function which I need to pass in order to get the app_context.

在我的 __ ini __.py 中，我有这个:

# application/__init__.py

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_restful import Api
from application.resources.product import Product, Products
from application.resources.offer import Offer, Offers  # HERE IS THE PROBLEM

api = Api()
db = SQLAlchemy()

api.add_resource(Product, "/product/<string:name>")  # GET, POST, DELETE, PUT to my local database
api.add_resource(Products, "/products")  # GET all products from my local database
api.add_resource(Offer, "/offer/<int:id>")  # POST call to the external Offers API microservise
api.add_resource(Offers, "/offers")  # GET all offers from my local database


def create_app(config_filename=None):
    """ Initialize core application. """
    app = Flask(__name__, instance_relative_config=False)
    app.config.from_object("config.Config")

    db.init_app(app)
    api.init_app(app)

    with app.app_context():
        db.create_all()

        return app

问题出在这一行:

from application.resources.offer import Offer, Offers  # HERE IS THE PROBLEM

因为在那个模块中，我有:

because in that module, I have:

#application/resources/offer.py 

from flask_restful import Resource
from application.models.offer import OfferModel  # IMPORTING OFFER MODEL

依次导入 application/models/offer.py ，其中我有关键部分:

which in turn imports application/models/offer.py where I have the critical part:

#application/models/offer.py

import requests
# from flask import current_app as app 
from application import create_app  # THIS CAUSES THE CIRCULAR IMPORT ERROR
from sqlalchemy.exc import OperationalError

app = create_app() # I NEED TO CREATE THE APP IN ORDER TO GET THE APP CONTEXT BECASE IN THE CLASS I HAVE SOME FUNCTIONS THAT NEED IT

class OfferModel(db.Model):
    """ Data model for offers. """
    # some code to instantiate the class... + other methods..

    # THIS IS ONE OF THE METHODS THAT NEED APP_CONTEXT OR ELSE IT WILL ERROR OUT
    @classmethod
    def update_offer_price(cls):
        """ Call offers api to get new prices. This function will run in a separated thread in a scheduler. """
        with app.app_context():
            headers = {"Bearer": app.config["MS_API_ACCESS_TOKEN"]}
            for offer_id in OfferModel.offer_ids:
                offers_url = app.config["MS_API_OFFERS_BASE_URL"] + "/products/" + str(offer_id) + "/offers"
                res = requests.get(offers_url, headers=headers).json()
                for offer in res:
                    try:
                        OfferModel.query.filter_by(offer_id=offer["id"]).update(dict(price=offer["price"]))
                        db.session.commit()
                    except OperationalError:
                        print("Database does not exists.")
                        db.session.rollback()

我尝试使用从flask导入current_app作为app 的烧瓶中获取的上下文，但它不起作用.我不知道为什么不足以将current_app作为应用程序传递并获取上下文，因为它现在迫使我通过create_app应用程序工厂，这会导致循环导入问题.

I have tried to use from flask import current_app as app to get the context, it did not work. I don't know why it was not sufficient to pass current_app as app and get the context because it now forces me to pass the create_app application factory which causes the circular import problem.

推荐答案

好的，这就是我解决的方法.我创建了一个新文件endpoints.py，在其中放置了所有的Api资源

ok so this is how I solved it. I made a new file endpoints.py where I put all my Api resources

# application/endpoints.py    

from application import api
from application.resources.product import Product, Products
from application.resources.offer import Offer, Offers

api.add_resource(Product, "/product/<string:name>")  # GET, POST, DELETE, PUT - calls to local database
api.add_resource(Products, "/products")  # GET all products from local database.
api.add_resource(Offer, "/offer/<int:id>")  # POST call to the Offers API microservice.
api.add_resource(Offers, "/offers")  # GET all offers from local database

然后在init.py中，将其导入到最底部.

Then in init.py I import it at the very bottom.

# aplication/__init__.py

from flask import Flask
from flask_restful import Api
from db import db

api = Api()


def create_app():
    app = Flask(__name__, instance_relative_config=False)
    app.config.from_object("config.Config")
    db.init_app(app)
    api.init_app(app)
    
    with app.app_context():
        from application import routes
        db.create_all()

        return app


from application import endpoints # importing here to avoid circular imports

它不是很漂亮，但是可以.

It is not very pretty but it works.

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