Django model模型, since 2022-01-14

(2022.01.14 Fri)
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ORM

ORM, a.k.a., Object Relational Mapping，用于实现面向对象编程里面不同类型系统之间的数据转换。

生成model

(2022.01.20 Thur)
使用模型前，先创建一个专门的app，设置app的名字是db，指令如下

$ pwd
 /project_name
$ django-admin startapp db

此时会项目根目录下会出现新的文件夹db，其中包含admin.py, views.py, models.py等文件。

修改db/models.py文件

from unittest.util import _MAX_LENGTH
from django.db import models

# Create your models here.
class ModelX(models.Model):
    # primary_id = AutoField()
    date_start = models.DateField()
    date_end = models.DateField()
    nation = models.CharField(max_length=30)
    spot = models.CharField(max_length=30)

修改/project_name/project_name/settings.py文件，加入db app。

...
INSTALLED_APPS = [
    ...,
    'db',
]

在根目录运行下列指令创建数据库

$ python manage.py makemigration db
$ python manage.py migrate db

在根目录下进入Django的shell环境，并手动输入新数据

$ python manage.py shell
...
In [1]: from db.models import ModelX

In [2]: ModelX.objects.create(date_start='2012-12-23', date_end='2012-12-27', nati
   ...: on='Spain', spot='Barcelona')
Out[2]: <ModelX: ModelX object (1)>

In [3]: ModelX.objects.get(spot='Barcelona')
Out[3]: <ModelX: ModelX object (1)>

In [4]: ModelX.objects.create(date_start='2021-11-04', date_end='2021-11-04', nati
   ...: on='China', spot='Suzhou')
Out[4]: <ModelX: ModelX object (2)>

通过下面指令查看数据表中的所有字段

In [5]: [term.name for term in ModelX._meta.fields]
Out[5]: ['id', 'date_start', 'date_end', 'nation', 'spot']

数据添加完成。之后修改根目录的urls.py，添加如下代码

from db import urls
urlpatterns = [
    ...
    path('db/', include(urls)),
]

在db文件夹的urls.py中添加如下

from django.contrib import admin
from django.urls import path, re_path, include
from . import views
 
urlpatterns = [
    path('query-all/', views.query_all),
]

在db文件夹的views.py中添加方法

from django.shortcuts import render, redirect
from db.models import ModelX as mx
...
def query_all(requests):
    db = mx.objects.all()
    records_cntr = len(db)
    fields_list = [term.name for term in mx._meta.fields]
    res = []
    for i in range(records_cntr):
        ob = mx.objects.get(id=i+1)
        ts = f"""response {i}: """
        ts += f"""id={str(ob.id)}, date start={str(ob.date_start)}, 
        date end={str(ob.date_end)}, nation={ob.nation}, spot={ob.spot}"""
        res.append(ts)
    return HttpResponse('\n'.join(res))

此时打开页面localhost:8000/db/query-all即可返回数据结果。数据表达待调整。