如何建立一个具有不同模型的两个外键关系的模型

Question

I have made an app in which i have made three models as below:

from django.db import models

class Class_Mgmt(models.Model):
    class_name = models.CharField(max_length=8,null=False,blank=False)

    def __str__(self):
        return self.class_name


class Section_Mgmt(models.Model):
    stu_class=models.ForeignKey(Class_Mgmt)
    section_name=models.CharField(max_length=1,null=False,blank=False)

    def __str__(self):
        return self.section_name

class Teacher_Mgmt(models.Model):
    teacher_name=models.CharField(max_length=50,null=False,blank=False)
    tea_class=models.ForeignKey(Class_Mgmt)
    tea_section=models.ForeignKey(Section_Mgmt)

    def __str__(self):
        return self.teacher_name

Here, Section_Mgmt class has a foreignKey relation with Class_Mgmt that means when i run the project and add a new section_name , then class_name will be selected from a drop-down list of all the existing classes. It is working well in the project. But, in the Teacher_Mgmt model, i want to do like this: When i enter a new teacher in my form, then when i select the existing class from the dropdown list, then it will only show the sections available on the selected class because, section_Mgmt model also has the foreign key relation with the class_Mgmt model.

At present, when i am running the project and enter a new teacher, and select a class from the dropdown showing all the existing classes,then is showing all the sections instead of showing only those sections available in that class.

Answer 1

Django does not have this functionality built in but you can use django-smart-selects . Just install this library and change the Teacher_Mgmt to the following code:

from smart_selects.db_fields import ChainedForeignKey 

class Teacher_Mgmt(models.Model):
    teacher_name=models.CharField(max_length=50,null=False,blank=False)
    tea_class=models.ForeignKey(Class_Mgmt)

    tea_section=ChainedForeignKey(
        Section_Mgmt, 
        chained_field="tea_class",
        chained_model_field="tea_class", 
        show_all=False, 
        auto_choose=True
    )

    def __str__(self):
        return self.teacher_name