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Django Tutorial
Django Tutorial Part 3: Using models
Django Tips #4 Automatic DateTime Fields
How to trigger function in Django app
Get inspiration from this link:
How to run function if model instance field is equal to inplay (Django)
Be clear about what method to use after reading this:
Trigger a function in a Django model every time its variables change
django signals
In fact, it already use created to denote new object, but I didn’t notice it back to that time, and searched other links to achieving only trigger on new objects.
Django: how can I tell if the post_save signal triggers on a new object?
There is a
creatednamed argument which will be set toTrueif it’s a new object.
This is the Documentation of Signals
More examples here
Django signal 信号机制的使用： 中文介绍
python 之 Django框架(APP和ORM的使用)：中文介绍
理解Django的makemigrations和migrate
在你改动了 model.py的内容之后执行下面的命令：
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python manage.py makemigrations
相当于在该app下建立 migrations目录，并记录下你所有的关于modes.py的改动，比如0001_initial.py， 但是这个改动还没有作用到数据库文件
你可以手动打开这个文件，看看里面是什么。当makemigrations之后产生了0001_initial.py 文件，你可以查看下该migrations会对应于什么样子的SQL命令，使用如下命令:
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python manage.py sqlmigrate theapp 0001
在makemigrations之后执行命令：
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python manage.py migrate
将该改动作用到数据库文件，比如产生table，修改字段的类型等。
