Flask-上下文管理

1. 

案例1  

class Foo(object):

    def __str__(self):
        return "asdf"

    def __getattr__(self, item):
        return "99"

    def __getitem__(self, item):
        return "87"
    def __add__(self, other):
        return other +1


obj =Foo()
print(obj) #asdf
print(obj.x) # 99
print(obj.y) # 99
print(obj["x"]) #87
print(obj["y"]) #87
print(obj +8) #9

案例二

py1（s11）

DATA ={
    "request":{
        "x1":"xxx1",
        "x2":"xxx2"
    }
}

class LocalProxy(object):

    def get_dict(self):
        return DATA['request']

    def __str__(self):
        return "asdf"

    def __getattr__(self, item):

        data_dict=self.get_dict()
        return data_dict[item]

    def __getitem__(self, item):

        data_dict =self.get_dict()
        return data_dict[item]

    def __add__(self, other):
        return other +1


request =LocalProxy()  #实例化request对象

session =LocalProxy()

py2

from s11 import request
print(request)
print(request.x1)
print(request.x2)

执行py2 打印结果为

asdf
xxx1
xxx2

案例三（案例二的改进版）

DATA ={
    "request":{
        "method":"GET",
        "form":{}
    },
    "session":{
        "user":"alex",
        "age":"19",
    }
}

class LocalProxy(object):

    def __init__(self,key):   #此对象增加初始化方法，定义属性 ,将此属性传到实例化方法中.
        self.key =key

    def get_dict(self):
        return DATA[self.key]

    def __str__(self):
        return "asdf"

    def __getattr__(self, item):

        data_dict=self.get_dict()
        return data_dict[item]

    def __getitem__(self, item):

        data_dict =self.get_dict()
        return data_dict[item]

    def __add__(self, other):
        return other +1


request =LocalProxy("request")
session =LocalProxy("session")

执行如下文件.

from s11 import request,session

print(request.method)  #GET
print(request.form)    #{}

print(session.user)    #alex
print(session.age)     #19

from flask import Flask,request,session

app = Flask(__name__)


@app.route('/index')
def index():
    # 1. request是LocalProxy对象
    # 2. 对象中有method、执行__getattr__
    print(request.method)
    # request['method']
    # request + 1

    # 1. session是LocalProxy对象
    # 2. LocalProxy对象的__setitem__
    session['x'] = 123

    return "Index"


if __name__ == '__main__':
    app.run()
    # app.__call__
    # app.wsgi_app

"""
第一阶段：请求到来
    将request和Session相关数据封装到ctx=RequestContext对象中。
    再通过LocalStack将ctx添加到Local中。
    __storage__ = {
        1231:{'stack':[ctx(request,session)]}
    }
第二阶段：视图函数中获取request或session
    方式一：直接找LocalStack获取
            from flask.globals import _request_ctx_stack
            print(_request_ctx_stack.top.request.method)
            
    方式二：通过代理LocalProxy(小东北)获取
            from flask import Flask,request
            print(request.method)
            
"""