Django Starter Design Model

define model class

• There is a data table, there is a model class corresponding to it
• Open the models.py file and define the model class
• Import packages from django.db import models
• Model classes inherit from the models.Model class
• Description: There is no need to define the primary key column, it will be added automatically when it is generated, and the value will grow automatically
• When the object is output, the str method of the object is called

E.g:

• This example completes the maintenance of the "Book-Hero" information, and needs to store two kinds of data: books, heroes
• Book table structure design:
  • 表名：BookInfo
  • Book name: btitle
  • Book published: bpub_date
• Hero table structure design:
  • Table name: HeroInfo
  • Hero name: hname
  • Hero gender: hgender
  • Hero Profile: hcontent
  • Belongs to the book: hbook
• The book-hero relationship is one-to-many

Relevant code:

from django.db import models

class BookInfo(models.Model):
    btitle = models.CharField(max_length=20)
    bpub_date = models.DateTimeField()
    def _ _str_ _(self):
        return "%d" % self.pk

class HeroInfo(models.Model):
    hname = models.CharField(max_length=20)
    hgender = models.BooleanField()
    hcontent = models.CharField(max_length=100)
    hBook = models.ForeignKey('BookInfo')
    def _ _str_ _(self):
        return "%d" % self.pk

Then generate the data table:

• Activate the model: Edit the settings.py file and add the booktest application to the installed_apps of settings.py
• 
  

        

• Generate migration files: generate sql statements based on model classes

python manage.py makemigrations

• Migration files are generated into the application's migrations directory

        

• Execute migration: execute sql statement to generate data table

python manage.py migrate

test data manipulation

• Enter the python shell for simple model API exercises

python manage.py shell

• After entering the shell, the prompt is as follows:

        

• Import the required packages:

from booktest.models import BookInfo,HeroInfo
from django.utils import timezone
from datetime import *

• Query all book information:

BookInfo.objects.all()

• New book information:

b = BookInfo()
b.btitle="射雕英雄传"
b.bpub_date=datetime(year=1990,month=1,day=10)
b.save()

• Find book information:

b=BookInfo.objects.get(pk=1)

• Output book information:

b
b.id
b.btitle

• Edit book information:

b.btitle=u"天龙八部"
b.save()

• Delete book information:

b.delete()

Operations on Associated Objects

• For HeroInfo, it can be done as above
• Add, pay attention to adding associated objects

h=HeroInfo()
h.htitle=u'郭靖'
h.hgender=True
h.hcontent=u'降龙十八掌'
h.hBook=b
h.save()

• Get the associated collection: return all heroes of the current book object

b.heroinfo_set.all()

• For a HeroInfo to exist, there must be a BookInfo object that provides the data to create the association:

h=b.heroinfo_set.create(htitle=u'黄蓉',hgender=False,hcontent=u'打狗棍法')
h