烧瓶蓝色打印before_first_request

问题描述

是否可以在第一次请求特定的蓝图之前运行一个函数？

  @ my_blueprint.before_first_request 
 def init_my_blueprint（）：
 print'yes'
  

目前这将产生以下错误：

pre $ AttributeError：'Blueprint'对象没有属性'before_first_request'


解决方案

Blueprint相当于：

  @ my_blueprint.before_app_first_request 
 def init_my_blueprint（）：
 print'yes'
  

该名称反映它在任何请求之前调用，而不仅仅是特定于此蓝图的请求。

对于仅仅运行代码没有任何钩子首先要求你的蓝图处理。您可以使用测试它是否已经运行：

  from线程导入锁定
 
 my_blueprint._before_request_lock = Lock（）
 my_blueprint._got_first_request = False 
 
 @ my_blueprint.before_request 
 def init_my_blueprint（）：
 if my_blueprint ._got_first_request：
返回
 with my_blueprint._before_request_lock：
 if my_blueprint._got_first_request：
 return 
 my_blueprint._got_first_request = True 
 
＃first请求，执行你所需要的。 
 print'yes'
  

这个模拟Flask在这里的功能。锁定是必要的，因为单独的线程可以争先恐后。

Is it possible to run a function before the first request to a specific blueprint?

@my_blueprint.before_first_request
def init_my_blueprint():
    print 'yes'

Currently this will yield the following error:

AttributeError: 'Blueprint' object has no attribute 'before_first_request'

解决方案

The Blueprint equivalent is called @Blueprint.before_app_first_request:

@my_blueprint.before_app_first_request
def init_my_blueprint():
    print 'yes'

The name reflects that it is called before any request, not just a request specific to this blueprint.

There is no hook for running code for just the first request to be handled by your blueprint. You can simulate that with a @Blueprint.before_request handler that tests if it has been run yet:

from threading import Lock

my_blueprint._before_request_lock = Lock()
my_blueprint._got_first_request = False

@my_blueprint.before_request
def init_my_blueprint():
    if my_blueprint._got_first_request:
        return
    with my_blueprint._before_request_lock:
        if my_blueprint._got_first_request:
            return 
        my_blueprint._got_first_request = True

        # first request, execute what you need.
        print 'yes'

This mimics what Flask does here; locking is needed as separate threads could race to the post to be first.

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