Django message组件-五八三

使用message组件要在seetings中配置

①INSTALLED_APPS (项目需要什么功能都放在这既可以有数据库,又可以写代码,html文件,和自己写的APP一个道理)

②MIDDLEWARE 中间件 (请求进来做什么,请求走的时候做什么)

③TEMPLATES (模板,在html页面中操作方便)

④第四个位置可以放在任意地方有三种配置(将数据保存在cookie中或session中,或者全部保存)

使用方法

设置值

第一个参数request .第二个参数消息的级别,messages.SUCCESS不一定要这么写.第三个参数,自己写具体的参数. 以列表的形式存在

1 from django.contrib import messages
2 messages.add_message(reqeust, messages.SUCCESS, "删除成功")
3 messages.add_message(reqeust, messages.ERROR, "删除失败")

在视图中读取值(使用python代码) 循环读取到messages, 读取到的同时并删除 (类里面写的iter方法所以可以循环)

1 from django.contrib.messages.api import get_messages
2 messages = get_messages(request)
3 for msg in messages:
4     print(msg)

使用html代码读取值

<ul>
    {% for message in messages %}
        <li>{{ message.tags }} {{ message }}</li>
    {% endfor %}
</ul>

源码分析

message是一个对象(包裹),可以包裹很多数据

 1 class Message:
 2     """
 3     Represent an actual message that can be stored in any of the supported
 4     storage classes (typically session- or cookie-based) and rendered in a view
 5     or template.
 6     """
 7 
 8     def __init__(self, level, message, extra_tags=None):
 9         self.level = int(level)
10         self.message = message
11         self.extra_tags = extra_tags
12 
13     def _prepare(self):
14         """
15         Prepare the message for serialization by forcing the ``message``
16         and ``extra_tags`` to str in case they are lazy translations.
17         """
18         self.message = str(self.message)
19         self.extra_tags = str(self.extra_tags) if self.extra_tags is not None else None
20 
21     def __eq__(self, other):
22         if not isinstance(other, Message):
23             return NotImplemented
24         return self.level == other.level and self.message == other.message
25 
26     def __str__(self):
27         return str(self.message)
28 
29     @property
30     def tags(self):
31         return ' '.join(tag for tag in [self.extra_tags, self.level_tag] if tag)
32 
33     @property
34     def level_tag(self):
35         return LEVEL_TAGS.get(self.level, '')

View Code

request,level,message分别对应设置值时候的参数,extra_tags=”:可以自己写点东西,一般不用写.fail_silently=False,是在if not fail_silently 做的一个异常处理,也就是说如果有异常了安安静静的在那不要报错.

重点: messages = request._messages 在request中读取到了一个对象,return messages.add(level, message, extra_tags) 调用了messages.add,把这个三个参数传过去了.

request_messages是在’django.contrib.messages.middleware.MessageMiddleware’ 这个中间件中定义的,看是在第四个位置中哪个存储的对象,SessionStorage对象(第四个位置设置的哪个就是那个对象)

所以messages = request._messages就是声明了一个SessionStorage的对象(第四个位置设置的哪个就是那个对象),SessionStorage源码中实例化了这个对象,下面有调用了messages.add(level, message, extra_tags)方法,SessionStorage这个类中没有message.add方法,在父类BaseStorage中,接收了三个参数def add(self, level, message, extra_tags=”).最后封装给了message = Message(level, message, extra_tags=extra_tags), 总而言之绕了一圈,最终传入进来的值都会封装给Message对象

def add_message(request, level, message, extra_tags='', fail_silently=False):
    """
    Attempt to add a message to the request using the 'messages' app.
    """
    try:
　　　　#SessionStorage的对象(第四个位置设置的哪个就是那个对象)

        messages = request._messages
"""
    except AttributeError:
        if not hasattr(request, 'META'):
            raise TypeError(
                "add_message() argument must be an HttpRequest object, not "
                "'%s'." % request.__class__.__name__
            )
        if not fail_silently:
            raise MessageFailure(
                'You cannot add messages without installing '
                'django.contrib.messages.middleware.MessageMiddleware'
            )
"""
    else:
        return messages.add(level, message, extra_tags)

SessionStorage源码中实例化了这个对象

SessionStorage父类中

Message中

 1 class Message:
 2     """
 3     Represent an actual message that can be stored in any of the supported
 4     storage classes (typically session- or cookie-based) and rendered in a view
 5     or template.
 6     """
 7 
 8     def __init__(self, level, message, extra_tags=None):
 9         self.level = int(level)
10         self.message = message
11         self.extra_tags = extra_tags
12 
13     def _prepare(self):
14         """
15         Prepare the message for serialization by forcing the ``message``
16         and ``extra_tags`` to str in case they are lazy translations.
17         """
18         self.message = str(self.message)
19         self.extra_tags = str(self.extra_tags) if self.extra_tags is not None else None
20 
21     def __eq__(self, other):
22         if not isinstance(other, Message):
23             return NotImplemented
24         return self.level == other.level and self.message == other.message
25 
26     def __str__(self):
27         return str(self.message)
28 
29     @property
30     def tags(self):
　　　　　　# 自己的tag和通过extra传进来的tag都传进来通过空格拼接
31         return ' '.join(tag for tag in [self.extra_tags, self.level_tag] if tag)
32 
33     @property
34     def level_tag(self):
35         return LEVEL_TAGS.get(self.level, '')