Flask.url_for() 错误:尝试在没有推送应用程序上下文的情况下生成 URL [英] Flask.url_for() error: Attempted to generate a URL without the application context being pushed

问题描述

我有一个微不足道的应用程序，我试图在其中重定向网站图标:

I have a trivial app where I'm trying to redirect the favicon per:

http://flask.pocoo.org/docs/0.10/patterns/favicon/

app = flask.Flask(__name__)
app.add_url_rule('/favicon.ico', redirect_to=flask.url_for('static', filename='favicon.ico'))

但这失败了:

RuntimeError: Attempted to generate a URL without the application context being pushed. This has to be executed when application context is available.

所以，猜测，我试试这个:

So, guessing, I try this:

app = flask.Flask(__name__)
with app.app_context():
    flask.current_app.add_url_rule('/favicon.ico', redirect_to=flask.url_for('static', filename='favicon.ico'))

但得到一个不同的错误:

But get a different error:

RuntimeError: Application was not able to create a URL adapter for request independent URL generation. You might be able to fix this by setting the SERVER_NAME config variable.

这是怎么回事?

推荐答案

根据 文档:

默认情况下，设置 SERVER_NAME 也会启用 URL 生成，无需请求上下文但具有应用程序上下文.

Setting a SERVER_NAME also by default enables URL generation without a request context but with an application context.

由于您使用的是 app_context，您可以设置 SERVER_NAME 配置值.

since you're using app_context, you may set the SERVER_NAME Configuration Value.

顺便说一下，作为 doc:Adding a favicon 说:

By the way, as the doc:Adding a favicon says:

<link rel="shortcut icon" href="{{ url_for('static', filename='favicon.ico') }}">

对于大多数浏览器来说，上面这行应该足够了，我们不需要做任何其他事情.

the above line should be enough for most browsers, we don't have to do any other things.

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