Django小技巧14: messages 框架

Posted October 30, 2018

翻译整理自: simpleisbetterthancomplex.com

让用户知道应用程序发生了什么，是个极好的用户体验。让应用程序和用户之间能够有个很好的『交流』是个不错的选择。

设想一下下面场景:

用户: 点击保存按钮
应用程序：什么都没有发生
所以是否保存了数据？用户并不知道
这时一些急性子就疯狂的点击，点击，点击...

所以，要让用户不要慌...

配置

默认情况下，Django 项目内置了messages框架, 如果你没有更改这些配置，只需要跳到下一节。如果有改动，按照下面这样设置：

INSTALLED_APPS
- django.contrib.messages
MIDDLEWARE 或者 MIDDLEWARE_CLASSES(老版本)
- django.contrib.sessions.middleware.SessionMiddleware
- django.contrib.messages.middleware.MessageMiddleware
TEMPLATES
- context_processors
  - django.contrib.messages.context_processors.messages

消息级别和标签

Constant	Level	Tag	Purpose
DEBUG	10	debug	开发相关的消息
INFO	20	info	用户级别消息
SUCCESS	25	success	一个操作的成功消息
WARNING	30	warning	失败但非迫在眉睫的消息
ERROR	40	errror	操作未成功或发生错误

默认情况下， Django 只会显示 level >= 20 (INFO)的消息，如果显示DEBUG消息，可以在设置中:

settings.py

from django.contrib.messages import constants as message_constants
MESSAGE_LEVEL = message_constants.DEBUG

<\>Python

为了避免遇到导入循环，可以直接设置 level.

MESSAGE_LEVEL = 10  # DEBUG

<\>Python

使用

在视图里面必要的地方添加，触发消息的逻辑，在模板里面添加显示的代码，就可以使用消息啦

views.py

from django.contrib import messages

@login_required
def password(request):
    if request.method == 'POST':
        form = PasswordChangeForm(request.user, request.POST)
        if form.is_valid():
            form.save()
            update_session_auth_hash(request, form.user)
            messages.success(request, 'Your password was updated successfully!')  # <-
            return redirect('settings:password')
        else:
            messages.warning(request, 'Please correct the error below.')  # <-
    else:
        form = PasswordChangeForm(request.user)
    return render(request, 'profiles/change_password.html', {'form': form})

<\>Python

然后template中

{% if messages %}
  <ul class="messages">
    {% for message in messages %}
      <li class="{{ message.tags }}">{{ message }}</li>
    {% endfor %}
  </ul>
{% endif %}

<\>Django

如果添加成功了，则输出的 html 应该是这样呢, 可以看到实际上标签应该和你的用户美化messsage的 css 对应。

<ul class="messages">
  <li class="success">Your password was updated successfully!</li>
</ul>

<\>Html

你可以对 message，添加额外的标签:

messages.success(request, 'Your password was updated successfully!', extra_tags='alert')

<\>Python

输出html 为:

<ul class="messages">
  <li class="success alert">Your password was updated successfully!</li>
</ul>

<\>Html

内置方法介绍:

messages.debug(request, 'Total records updated {0}'.format(count))
messages.info(request, 'Improve your profile today!')
messages.success(request, 'Your password was updated successfully!')
messages.warning(request, 'Please correct the error below.')
messages.error(request, 'An unexpected error occured.')

# Or...

messages.add_message(request, messages.DEBUG, 'Total records updated {0}'.format(count))
messages.add_message(request, messages.INFO, 'Improve your profile today!')

# Useful to define custom levels:
CRITICAL = 50
messages.add_message(request, CRITICAL, 'A very serious error ocurred.')

<\>Python

和Bootstrap结合代码片段

messages.html

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

<\>Django

settings.py

Bootstrap 中定义了如alert-info或者alert-success等alert-*的组件css. 所以我们需要更改下默认的 tags.

from django.contrib.messages import constants as messages

MESSAGE_TAGS = {
    messages.DEBUG: 'alert-info',
    messages.INFO: 'alert-info',
    messages.SUCCESS: 'alert-success',
    messages.WARNING: 'alert-warning',
    messages.ERROR: 'alert-danger',
}

<\>Python

base.html

然后把messages.html添加到需要显示的地方:

<!doctype html>
<html>
  <head>
    <meta charset="utf-8">
    <title>Simple is Better Than Complex</title>
  </head>
  <body>
    {% include 'partials/header.html' %}
    <main>
      <div class="container">
        {% include 'partials/messages.html' %}
        {% block content %}
        {% endblock %}
      </div>
    </main>
    {% include 'partials/footer.html' %}
  </body>
</html>

<\>Django

阅读更多关于messages框架的文档. Django Documentation

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#Django小技巧