Posted on by Mingyu Zhu

[实验] Django 自定义逻辑添加 （通过自定义 manager 管理器实现） （一次性完成多对多表数据的插入）

注意：

本实验是接着 《Django 数据展示（多对多版）》而继续的

Django
数据展示
（多对多版）

正文：

步骤一：在没有自定义 manager 管理器的情况下尝试一次性完成多对多表数据的插入

1.1 进入相应的 Django 环境

>>> import os,django
>>> os.environ.setdefault("DJANGO_SETTINGS_MODULE", "mysite.settings")
'mysite.settings'
>>> django.setup()
>>> from user.models import *

1.2 在没有自定义 manager 管理器的情况下尝试一次性完成多对多表数据的插入

>>> Student.objects.create(sname='lili',clazz='Class1',course=('Python','Shell'))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/zhumingyu/Code/Django/mtwo/django_env/lib/python3.8/site-packages/django/db/models/manager.py", line 85, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/Users/zhumingyu/Code/Django/mtwo/django_env/lib/python3.8/site-packages/django/db/models/query.py", line 451, in create
    obj = self.model(**kwargs)
  File "/Users/zhumingyu/Code/Django/mtwo/django_env/lib/python3.8/site-packages/django/db/models/base.py", line 503, in __init__
    raise TypeError("%s() got an unexpected keyword argument '%s'" % (cls.__name__, kwarg))
TypeError: Student() got an unexpected keyword argument 'clazz'

（
补充：
（1）这里数据插入失败
（2）按正常顺序应该是先插入班级 clazz，之后再插入学生 student，之后再插入课程 course，之后再去插入中间表
）

1.3 退出相应的 Django 环境

>>> quit();

步骤二：确认要插入的数据和预期的一致（可选）

2.1 创建 1 个自定义 manager 管理器的类

将 mysite/test/models.py 中的以下内容:

......
class Clazz(models.Model):
    cno = models.AutoField(primary_key=True)
    cname = models.CharField(max_length=30)

    def __str__(self):
        return u'Clazz:%s'%self.cname

class Course(models.Model):
    course_no = models.AutoField(primary_key=True)
    course_name = models.CharField(max_length=30)

    def __str__(self):
        return u'Course:%s'%self.course_name

class Student(models.Model):
    sno = models.AutoField(primary_key=True)
    sname = models.CharField(max_length=30)
    cls = models.ForeignKey(Clazz,on_delete=models.CASCADE)
    cour = models.ManyToManyField(Course)

    def __str__(self):
        return u'Student:%s'%self.sname

# Get class object according to class name
def getCls(cname):
    try:
        cls = Clazz.objects.get(cname=cname)
    except Clazz.DoesNotExist:
        cls = Clazz.objects.create(cname=cname)
    return cls

def getCourseList(*coursenames):
    courseList = []

    for cn in coursenames:
        try:
            c = Course.objects.get(course_name=cn)
        except Course.DoesNotExist:
            c = Course.objects.create(course_name=cn)
        courseList.append(c)

    return courseList

def registerStu(sname,cname,*coursenames):
    #1. Get class objects
    cls = getCls(cname)
    #2. Gets the list of course objects
    courseList = getCourseList(*coursenames)
    #3. Insert student table data
    try:
        stu = Student.objects.get(sname=sname)
    except Student.DoesNotExist:
        stu = Student.objects.create(sname=sname,cls=cls)
    #4. Insert intermediate table data
    stu.cour.add(*courseList)

    return True

修改为：

......
from django.db import models
from django.db.models.manager import Manager

# Create your models here.
class Clazz(models.Model):
    cno = models.AutoField(primary_key=True)
    cname = models.CharField(max_length=30)

    def __str__(self):
        return u'Clazz:%s'%self.cname

class Course(models.Model):
    course_no = models.AutoField(primary_key=True)
    course_name = models.CharField(max_length=30)

    def __str__(self):
        return u'Course:%s'%self.course_name

class CustomManager(Manager):
    def create(self, **kwargs):
        print(kwargs)

class Student(models.Model):
    sno = models.AutoField(primary_key=True)
    sname = models.CharField(max_length=30)
    cls = models.ForeignKey(Clazz,on_delete=models.CASCADE)
    cour = models.ManyToManyField(Course)

    objects = CustomManager()

    def __str__(self):
        return u'Student:%s'%self.sname

# Get class object according to class name
def getCls(cname):
    try:
        cls = Clazz.objects.get(cname=cname)
    except Clazz.DoesNotExist:
        cls = Clazz.objects.create(cname=cname)
    return cls

def getCourseList(*coursenames):
    courseList = []

    for cn in coursenames:
        try:
            c = Course.objects.get(course_name=cn)
        except Course.DoesNotExist:
            c = Course.objects.create(course_name=cn)
        courseList.append(c)

    return courseList

def registerStu(sname,cname,*coursenames):
    #1. Get class objects
    cls = getCls(cname)
    #2. Gets the list of course objects
    courseList = getCourseList(*coursenames)
    #3. Insert student table data
    try:
        stu = Student.objects.get(sname=sname)
    except Student.DoesNotExist:
        stu = Student.objects.create(sname=sname,cls=cls)
    #4. Insert intermediate table data
    stu.cour.add(*courseList)

    return True

（补充：这里以添加一个显示自己所有键值对的 CustomManager(Manager) 对象并在 Student 类中使用 objects 调用为例）

2.2 进入相应的 Django 环境

>>> import os,django
>>> os.environ.setdefault("DJANGO_SETTINGS_MODULE", "mysite.settings")
'mysite.settings'
>>> django.setup()
>>> from user.models import *

2.3 确认要插入的数据和预期的一致

>>> Student.objects.create(sname='lili',clazz='Class1',course=('Python','Shell'))
{'sname': 'lili', 'clazz': 'Class1', 'course': ('Python', 'Shell')}

2.4 退出相应的 Django 环境

>>> quit();

步骤三：一次性完成多对多表数据的插入

3.1 创建 1 个自定义 manager 管理器的类

将 mysite/test/models.py 中的以下内容:

......
class Clazz(models.Model):
    cno = models.AutoField(primary_key=True)
    cname = models.CharField(max_length=30)

    def __str__(self):
        return u'Clazz:%s'%self.cname

class Course(models.Model):
    course_no = models.AutoField(primary_key=True)
    course_name = models.CharField(max_length=30)

    def __str__(self):
        return u'Course:%s'%self.course_name

class Student(models.Model):
    sno = models.AutoField(primary_key=True)
    sname = models.CharField(max_length=30)
    cls = models.ForeignKey(Clazz,on_delete=models.CASCADE)
    cour = models.ManyToManyField(Course)

    def __str__(self):
        return u'Student:%s'%self.sname

# Get class object according to class name
def getCls(cname):
    try:
        cls = Clazz.objects.get(cname=cname)
    except Clazz.DoesNotExist:
        cls = Clazz.objects.create(cname=cname)
    return cls

def getCourseList(*coursenames):
    courseList = []

    for cn in coursenames:
        try:
            c = Course.objects.get(course_name=cn)
        except Course.DoesNotExist:
            c = Course.objects.create(course_name=cn)
        courseList.append(c)

    return courseList

def registerStu(sname,cname,*coursenames):
    #1. Get class objects
    cls = getCls(cname)
    #2. Gets the list of course objects
    courseList = getCourseList(*coursenames)
    #3. Insert student table data
    try:
        stu = Student.objects.get(sname=sname)
    except Student.DoesNotExist:
        stu = Student.objects.create(sname=sname,cls=cls)
    #4. Insert intermediate table data
    stu.cour.add(*courseList)

    return True

修改为：

......
class Clazz(models.Model):
    cno = models.AutoField(primary_key=True)
    cname = models.CharField(max_length=30)

    def __str__(self):
        return u'Clazz:%s'%self.cname

class Course(models.Model):
    course_no = models.AutoField(primary_key=True)
    course_name = models.CharField(max_length=30)

    def __str__(self):
        return u'Course:%s'%self.course_name

class CustomManager(Manager):
    #Returns a class object
    def getClsObj(self,cname):
        try:
            cls = Clazz.objects.get(cname=cname)
        except Clazz.DoesNotExist:
            cls = Clazz.objects.create(cname=cname)
        return cls

    def getCourseList(self,*coursenames):
        cList = []
        for cn in coursenames:
            try:
                cour = Course.objects.get(course_name=cn)
            except Course.DoesNotExist:
                cour = Course.objects.create(course_name=cn)
            cList.append(cour)
        return cList

    def  create(self, **kwargs):
         clazz = kwargs.get('cls','')

         #Class information multi storage operation
         clas = self.getClsObj(clazz) 

         #Replace string with object
         #Student.objects.create(sname='',cls=clas)
         kwargs['cls'] = clas

         #Assign a separate value pair of course keys to course
         course = kwargs.pop('cour')

         #Storage operation of student information
         stu = Manager.create(self,**kwargs)

         #Total of the course information in storage
         courseList = self.getCourseList(*course)

         #The middle table of student course is stored in the database. An object or tuple can be unpacked automatically here
         stu.cour.add(*courseList)

class Student(models.Model):
    sno = models.AutoField(primary_key=True)
    sname = models.CharField(max_length=30)
    cls = models.ForeignKey(Clazz,on_delete=models.CASCADE)
    cour = models.ManyToManyField(Course)

    objects = CustomManager()

    def __str__(self):
        return u'Student:%s'%self.sname

# Get class object according to class name
def getCls(cname):
    try:
        cls = Clazz.objects.get(cname=cname)
    except Clazz.DoesNotExist:
        cls = Clazz.objects.create(cname=cname)
    return cls

def getCourseList(*coursenames):
    courseList = []

    for cn in coursenames:
        try:
            c = Course.objects.get(course_name=cn)
        except Course.DoesNotExist:
            c = Course.objects.create(course_name=cn)
        courseList.append(c)

    return courseList

def registerStu(sname,cname,*coursenames):
    #1. Get class objects
    cls = getCls(cname)
    #2. Gets the list of course objects
    courseList = getCourseList(*coursenames)
    #3. Insert student table data
    try:
        stu = Student.objects.get(sname=sname)
    except Student.DoesNotExist:
        stu = Student.objects.create(sname=sname,cls=cls)
    #4. Insert intermediate table data
    stu.cour.add(*courseList)

    return True

（补充：这里以创建一次性完成多对多表数据的插入的 manage 管理器为例）

3.2 进入相应的 Django 环境

(django_env) [root@python mysite]# python3
>>> import os,django
>>> os.environ.setdefault("DJANGO_SETTINGS_MODULE", "mysite.settings")
'mysite.settings'
>>> django.setup()
>>> from user.models import *

3.3 一次性完成多对多表数据的插入

>>> Student.objects.create(sname='lili',cls='Class4',cour=('CSS','JS'))

（
补充：这里
1) 第 1 步执行：objects = CustomManager()
2) 第 2 步执行：def create(self, **kwargs)
3) 第 3 步执行：clazz = kwargs.get(‘cls’,”)，这步的结果是 clazz = ‘Class4’
4) 第 4 步执行：clas = self.getClsObj(clazz)，这步的结果是如果 Class4 在数据库中不存在则插入此条数据，并让 clas = cls
5) 第 5 步执行：cours = kwargs.pop(‘cour’)，这步的结果是 cours = (‘CSS’,’JS’)
6) 第 6 步执行：stu = Manager.create(self, **kwargs)，这步的结果是 stu = Student.objects.create(sname=”,cls=clas)
7) 第 7 步执行：courseList = self.getCourseList(*course)，这步的结果是如果 course 元组里的元素不存在则在数据库里创建，并将所有 course 里的元素放在 courseList 空列表中
8) 第 8 步执行：stu.cour.add(*courseList)，这步的结果是将 courseList 里的元素插入 Student 类的 cour 字段对应的中间表里
）