中间件在django中触发错误两次

Question

我已经为应用程序创建了一些中间件，可以根据登录用户检查一些条件。

如果它失败了，它就会启动让用户知道的错误。

问题是错误在页面顶部出现两次。

中间件看起来像这样：

class RegistrationMiddleware(object):

    def __init__(self, get_response):
        self.get_response = get_response
        print("In init of middleware")

    def __call__(self, request):
        # Code to be executed for each request before
        # the view (and later middleware) are called.
        print("Pre-view middle")
        response = self.get_response(request)
        # Code to be executed for each request/response after
        # the view is called.
        print("Post-view middle")

        ...logic stuff....

        if invalid_entries:
            for problem_reg in invalid_entries:
                messages.error(
                    request, format_html(
                        """
                        Please either
                        remove or change this registration.
                        """ 
                        )
                    )
        print('end of view reutrning response')
        return response

错误在页面上显示两次。

我的控制台显示如下：

Starting development server at http://127.0.0.1:8000/
Quit the server with CONTROL-C.
In init of middleware
Pre-view middle
this is a test of the get_user method
Post-view middle
end of view reutrning response
[25/Feb/2019 09:48:46] "GET /registrations/ HTTP/1.1" 200 21860
[25/Feb/2019 09:48:46] "GET /static/styles.css HTTP/1.1" 200 7082
[25/Feb/2019 09:48:46] "GET /static/registrations/style.css HTTP/1.1" 200 2282
[25/Feb/2019 09:48:46] "GET /static/registrations/index.js HTTP/1.1" 200 1885
[25/Feb/2019 09:48:46] "GET /static/all.min.js HTTP/1.1" 200 3738182
Pre-view middle
Post-view middle
this is a test of the get_user method
end of view reutrning response
Not Found: /favicon.ico
[25/Feb/2019 09:48:47] "GET /favicon.ico HTTP/1.1" 404 2586

我不确定中间件100％是检查这样的错误的最佳解决方案，但我需要在应用程序的基本上每个视图上检查相同的代码，所以它似乎是正确的方法来处理这个问题。

我只是试图让它只是一次触发 - 在视图渲染之前或之后都很好，但我只需要它来显示一个错误。

    {% for message in messages %}
        <div class="alert alert-{{ message.tags }} alert-dismissible mt-4" role="alert">
            <button type="button" class="close" data-dismiss="alert" aria-label="Close">
                <span aria-hidden="true">&times;</span>
            </button>
            {{ message }}
        </div>
    {% endfor %}

Answer 1

以下逻辑：response = self.get_response(request)导致问题和不一致的行为 - 因为警报在视图之后被处理，反过来导致错误被加载到下一次刷新并冲洗和重复，并且大部分时间错误被重复。

在视图处理之前将其移动到修复问题并帮助使其保持一致。