在 Django 中链接 ManyToManyFields

Question

我的模型定义如下：

class Subject(models.Model):
    subject_id = models.IntegerField(primary_key=True)
    subject_name = models.CharField(max_length=20)

class Teacher(models.Model):
    teacher_id = models.CharField(max_length=10, primary_key=True)
    teacher_name = models.CharField(max_length=30)
    teacher_age = models.IntegerField()
    teacher_doj = models.DateField()
    subjects = models.ManyToManyField(Subject)

class TeacherScores(models.Model):
    co_id = models.CharField(primary_key = True, max_length=5)
    internal_score = models.IntegerField()
    external_score = models.IntegerField()
    teacher = models.ManyToManyField(Teacher)

下面显示了几个数据库条目

老师

+------------+--------------+-------------+-------------+
| teacher_id | teacher_name | teacher_age | teacher_doj |
+------------+--------------+-------------+-------------+
| AC23001    | Tina         |          32 | 2017-04-10  |
| AC23002    | Rina         |          31 | 2009-04-10  |
| AC23003    | Tom          |          35 | 2009-04-10  |
| AC23004    | Henry        |          56 | 2009-04-10  |
+------------+--------------+-------------+-------------+

主题

+------------+--------------+
| subject_id | subject_name |
+------------+--------------+
|          1 | English      |
|          2 | Hindi        |
|          3 | Sanskrit     |
|          4 | Math         |
|          5 | Physics      |
|          6 | Chemistry    |
|          7 | Biology      |
|          8 | History      |
|          9 | Civics       |
|         10 | Geography    |
|         11 | MoralScience |
|         12 | Algebra      |
+------------+--------------+

teacher_subject

+----+------------+------------+
| id | teacher_id | subject_id |
+----+------------+------------+
|  4 | AC23002    |          4 |
|  5 | AC23002    |          8 |
|  2 | AC23002    |         12 |
|  6 | AC23003    |          5 |
|  7 | AC23003    |          9 |
| 10 | AC23004    |          5 |
|  8 | AC23005    |          9 |
|  9 | AC23005    |         10 |
| 11 | AC23006    |         12 |
| 12 | AC23007    |          6 |
| 13 | AC23008    |          6 |
+----+------------+------------+

基本上，我想为他/她处理的每个科目的特定教师添加条目到 TeacherSCores 模型中。 在这里，我想修改 TeacherScores 模型，以便我可以包含每个科目的教师分数。 我尝试通过 Teacherscores 对象插入主题，但出现错误。

>>> t1 =  TeacherScores('C006','23','24',teacher__subject='Math')
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/usr/local/lib/python2.7/dist-packages/Django-1.11.5-py2.7.egg/django/db/models/base.py", line 572, in __init__
    raise TypeError("'%s' is an invalid keyword argument for this function" % list(kwargs)[0])
TypeError: 'teacher__subject' is an invalid keyword argument for this function
>>> t1 =  TeacherScores('C006','23','24',teacher__subjects='Math')
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/usr/local/lib/python2.7/dist-packages/Django-1.11.5-py2.7.egg/django/db/models/base.py", line 572, in __init__
    raise TypeError("'%s' is an invalid keyword argument for this function" % list(kwargs)[0])
TypeError: 'teacher__subjects' is an invalid keyword argument for this function

如何更改我的模型 - TeacherScores 以包含教师的 学科字段，前提是在教师和学科之间定义了 ManyToMany 字段，以及 TeacherScores 和 Teacher

Answer 1

您要做的是创建显式的TeacherSubject 类，用于模拟Teacher 和Subject 之间的M2M 关系。然后你可以在TeacherScores中引用它。

1。模型 M2M Teacher-Subject 关系使用 through 选项：

class TeacherSubject(models.Model):
    teacher = models.ForeignKey(Teacher, on_delete=models.CASCADE)
    subject = models.ForeignKey(Subject, on_delete=models.CASCADE)
    # extra fields ...

然后修改Teacher和TeacherScores使用TeacherSubject：

# Teacher:

subjects = models.ManyToManyField(Subject, through=TeacherSubject)

# TeacherScores:

teachersubject = models.ForeignKey(TeacherSubject)

2。明确引用TeacherSubject:

t1 =  TeacherScores('C006','23','24', teachersubject=some_teachersubject_instance)

详细描述here。