4 请求&＃xff08;request&＃xff09;
from flask import request
request接收了WSGI server 传递过来的 environ 字典变量&＃xff0c;并提供了很多常用的属性和方法可以使用&＃xff0c;比如请求的 method、path、args 等。
同时request还有一个特性——它不能被应用修改&＃xff0c;应用只能读取请求的数据。
---> 4.1 Request(RequestBase)
其中 from werkzeug.wrappers import Request as RequestBase
该类继承 werkzeug的 request后&＃xff0c;定义了一些 &＃64;property属性
---> werkzeug.wrappers:Request
class Request(BaseRequest, AcceptMixin, ETagRequestMixin,UserAgentMixin, AuthorizationMixin,CommonRequestDescriptorsMixin):"""Full featured request object implementing the following mixins:- :class:&＃96;AcceptMixin&＃96; for accept header parsing- :class:&＃96;ETagRequestMixin&＃96; for etag and cache control handling- :class:&＃96;UserAgentMixin&＃96; for user agent introspection- :class:&＃96;AuthorizationMixin&＃96; for http auth handling- :class:&＃96;CommonRequestDescriptorsMixin&＃96; for common headers"""
---> BaseRequest
class BaseRequest(object):def __init__(self, environ, populate_request&＃61;True, shallow&＃61;False):self.environ &＃61; environif populate_request and not shallow:self.environ[&＃39;werkzeug.request&＃39;] &＃61; selfself.shallow &＃61; shallow
主要就是传入了 self.environ 作为字段。
然后用 &＃64;cached_property 定义了一些属性&＃xff0c; 像 args&＃xff0c; form&＃xff0c; COOKIEs等等
---> cached_property
接下来我们看看 增强版的 property
class cached_property(property):"""A decorator that converts a function into a lazy property. Thefunction wrapped is called the first time to retrieve the resultand then that calculated result is used the next time you accessthe value.The class has to have a &＃96;__dict__&＃96; in order for this property towork."""# implementation detail: A subclass of python&＃39;s builtin property# decorator, we override __get__ to check for a cached value. If one# choses to invoke __get__ by hand the property will still work as# expected because the lookup logic is replicated in __get__ for# manual invocation.def __init__(self, func, name&＃61;None, doc&＃61;None):self.__name__ &＃61; name or func.__name__self.__module__ &＃61; func.__module__self.__doc__ &＃61; doc or func.__doc__self.func &＃61; funcdef __set__(self, obj, value):obj.__dict__[self.__name__] &＃61; valuedef __get__(self, obj, type&＃61;None):if obj is None:return selfvalue &＃61; obj.__dict__.get(self.__name__, _missing)if value is _missing:value &＃61; self.func(obj)obj.__dict__[self.__name__] &＃61; valuereturn value
这个装饰器同时也是实现了 __set__ 和 __get__ 方法的描述器。 访问它装饰的属性&＃xff0c;就会调用 __get__ 方法&＃xff0c;这个方法先在 obj.__dict__ 中寻找是否已经存在对应的值。如果存在&＃xff0c;就直接返回&＃xff1b;如果不存在&＃xff0c;调用底层的函数 self.func&＃xff0c;并把得到的值保存起来&＃xff0c;再返回。这也是它能实现缓存的原因&＃xff1a;因为它会把函数的值作为属性保存到对象中。 ---cizixs
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