Flask 7（钩子函数、g、config）

我就是我 2023-10-08 12:03 48阅读 0赞

#### Flask 钩子函数、四大内置对象 ####

*   *   *  1、钩子函数
         *   *  1.1、before\_request
             *  1.2、after\_request
         *  2、四大内置对象之g
         *  3、四大内置对象之config

#### 1、钩子函数 ####

钩子函数相当于中间件（面向切面编程）  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FfX2ludF9f_size_16_color_FFFFFF_t_70]  
先来看看django中间件的处理流程  
![在这里插入图片描述][20200223215506839.png]  
钩子函数实例：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FfX2ludF9f_size_16_color_FFFFFF_t_70 1]  
运行并访问  
![在这里插入图片描述][20200223222446411.png]  
在访问每个路由前就会执行这个钩子函数  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FfX2ludF9f_size_16_color_FFFFFF_t_70 2]

##### 1.1、before\_request #####

这里我们把钩子函数单独写成一个文件

先把视图里面的注释掉  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FfX2ludF9f_size_16_color_FFFFFF_t_70 3]  
写一个middleware.py文件  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FfX2ludF9f_size_16_color_FFFFFF_t_70 4]

from flask import request
    
    
    def load_middleware(app):
        @app.before_request
        def before():
            print("你正在访问：", request.url)

在init里面注册  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FfX2ludF9f_size_16_color_FFFFFF_t_70 5]  
运行并访问试试  
![在这里插入图片描述][20200223230348149.png]  
![在这里插入图片描述][2020022323035570.png]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FfX2ludF9f_size_16_color_FFFFFF_t_70 6]

##### 1.2、after\_request #####

after\_request必须带一个参数，必须要有return  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FfX2ludF9f_size_16_color_FFFFFF_t_70 7]

#### 2、四大内置对象之g ####

g可以用来跨视图函数传递数据， g对象在一次请求中的所有的代码的地方，都是可以使用的。  
例：

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FfX2ludF9f_size_16_color_FFFFFF_t_70 8]  
记得导包  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FfX2ludF9f_size_16_color_FFFFFF_t_70 9]  
![在这里插入图片描述][20200224180514900.png]

#### 3、四大内置对象之config ####

config只能在flask项目启动之后输出

先输出看看config  
视图  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FfX2ludF9f_size_16_color_FFFFFF_t_70 10]  
html  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FfX2ludF9f_size_16_color_FFFFFF_t_70 11]

<ul>
        {
        % for foo in config %}
            <li>{
        {
         foo }}</li>
        {
        % endfor %}
    
    </ul>

访问  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FfX2ludF9f_size_16_color_FFFFFF_t_70 12]  
显示全局的配置信息  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FfX2ludF9f_size_16_color_FFFFFF_t_70 13]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FfX2ludF9f_size_16_color_FFFFFF_t_70 14]  
在视图里获取  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FfX2ludF9f_size_16_color_FFFFFF_t_70 15]  
![在这里插入图片描述][20200224214049824.png]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FfX2ludF9f_size_16_color_FFFFFF_t_70 16]

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